--- a/browser/base/content/browser-pageActions.js
+++ b/browser/base/content/browser-pageActions.js
@@ -15,17 +15,17 @@ var BrowserPageActions = {
    * The main page action panel DOM node (DOM node)
    */
   get panelNode() {
     delete this.panelNode;
     return this.panelNode = document.getElementById("pageActionPanel");
   },
 
   /**
-   * The photonmultiview node in the main page action panel (DOM node)
+   * The panelmultiview node in the main page action panel (DOM node)
    */
   get multiViewNode() {
     delete this.multiViewNode;
     return this.multiViewNode = document.getElementById("pageActionPanelMultiView");
   },
 
   /**
    * The main panelview node in the main page action panel (DOM node)
@@ -229,17 +229,17 @@ var BrowserPageActions = {
     if (this._disablePanelAnimations) {
       panelNode.setAttribute("animate", "false");
     }
 
     let panelViewNode = null;
     let iframeNode = null;
 
     if (action.subview) {
-      let multiViewNode = document.createElement("photonpanelmultiview");
+      let multiViewNode = document.createElement("panelmultiview");
       panelViewNode = this._makePanelViewNodeForAction(action, true);
       multiViewNode.appendChild(panelViewNode);
       panelNode.appendChild(multiViewNode);
     } else if (action.wantsIframe) {
       iframeNode = document.createElement("iframe");
       iframeNode.setAttribute("type", "content");
       panelNode.appendChild(iframeNode);
     }

--- a/browser/base/content/browser.css
+++ b/browser/base/content/browser.css
@@ -66,38 +66,27 @@ toolbar[customizable="true"] {
 #toolbar-menubar[autohide="true"] {
   -moz-binding: url("chrome://browser/content/customizableui/toolbar.xml#toolbar-menubar-autohide");
 }
 
 panelmultiview {
   -moz-binding: url("chrome://browser/content/customizableui/panelUI.xml#panelmultiview");
 }
 
-photonpanelmultiview {
-  -moz-binding: url("chrome://browser/content/customizableui/panelUI.xml#photonpanelmultiview");
-}
-
 panelview {
   -moz-binding: url("chrome://browser/content/customizableui/panelUI.xml#panelview");
   -moz-box-orient: vertical;
 }
 
 panel[hidden] panelmultiview,
-panel[hidden] photonpanelmultiview,
 panel[hidden] panelview {
   -moz-binding: none;
 }
 
-panelview:not([mainview]):not([current]):not([in-transition]) {
-  transition: visibility 0s linear var(--panelui-subview-transition-duration);
-  visibility: collapse;
-}
-
-photonpanelmultiview panelview:not([current]):not([in-transition]) {
-  transition: none;
+panelview:not([current]):not([in-transition]) {
   visibility: collapse;
 }
 
 panelview[mainview] > .panel-header,
 panelview:not([title]) > .panel-header {
   display: none;
 }
 

--- a/browser/base/content/browser.xul
+++ b/browser/base/content/browser.xul
@@ -412,25 +412,25 @@
            photon="true"
            position="bottomcenter topright"
            tabspecific="true"
            noautofocus="true"
            copyURL-title="&pageAction.copyLink.label;"
            emailLink-title="&emailPageCmd.label;"
            sendToDevice-title="&pageAction.sendTabToDevice.label;"
            sendToDevice-notReadyTitle="&sendToDevice.syncNotReady.label;">
-      <photonpanelmultiview id="pageActionPanelMultiView"
-                            mainViewId="pageActionPanelMainView"
-                            viewCacheId="appMenu-viewCache">
+      <panelmultiview id="pageActionPanelMultiView"
+                      mainViewId="pageActionPanelMainView"
+                      viewCacheId="appMenu-viewCache">
         <panelview id="pageActionPanelMainView"
                    context="pageActionContextMenu"
                    class="PanelUI-subView">
           <vbox class="panel-subview-body"/>
         </panelview>
-      </photonpanelmultiview>
+      </panelmultiview>
     </panel>
     <panel id="pageActionFeedback"
            role="alert"
            type="arrow"
            hidden="true"
            flip="slide"
            position="bottomcenter topright"
            tabspecific="true"

--- a/browser/components/controlcenter/content/panel.inc.xul
+++ b/browser/components/controlcenter/content/panel.inc.xul
@@ -11,18 +11,18 @@
        onpopuphidden="gIdentityHandler.onPopupHidden(event);"
        orient="vertical">
 
   <broadcasterset>
     <broadcaster id="identity-popup-mcb-learn-more" class="text-link plain" value="&identity.learnMore;"/>
     <broadcaster id="identity-popup-insecure-login-forms-learn-more" class="text-link plain" value="&identity.learnMore;"/>
   </broadcasterset>
 
-  <photonpanelmultiview id="identity-popup-multiView"
-                        mainViewId="identity-popup-mainView">
+  <panelmultiview id="identity-popup-multiView"
+                  mainViewId="identity-popup-mainView">
     <panelview id="identity-popup-mainView"
                descriptionheightworkaround="true">
       <!-- Security Section -->
       <hbox id="identity-popup-security" class="identity-popup-section">
         <vbox class="identity-popup-security-content" flex="1">
           <label class="plain">
             <label class="identity-popup-headline identity-popup-host"></label>
             <label class="identity-popup-headline identity-popup-hostless" crop="end"/>
@@ -179,10 +179,10 @@
 
       <vbox id="identity-popup-securityView-footer">
         <!-- More Security Information -->
         <button label="&identity.moreInfoLinkText2;"
                 oncommand="gIdentityHandler.handleMoreInfoClick(event);"/>
       </vbox>
 
     </panelview>
-  </photonpanelmultiview>
+  </panelmultiview>
 </panel>

--- a/browser/components/customizableui/CustomizableUI.jsm
+++ b/browser/components/customizableui/CustomizableUI.jsm
@@ -1615,17 +1615,17 @@ var CustomizableUIInternal = {
     } else if (aWidget.type == "view") {
       let ownerWindow = aNode.ownerGlobal;
       let area = this.getPlacementOfWidget(aNode.id).area;
       let areaType = CustomizableUI.getAreaType(area);
       let anchor = aNode;
       if (areaType != CustomizableUI.TYPE_MENU_PANEL) {
         let wrapper = this.wrapWidget(aWidget.id).forWindow(ownerWindow);
 
-        let hasMultiView = !!aNode.closest("photonpanelmultiview,panelmultiview");
+        let hasMultiView = !!aNode.closest("panelmultiview");
         if (wrapper && !hasMultiView && wrapper.anchor) {
           this.hidePanelForNode(aNode);
           anchor = wrapper.anchor;
         }
       }
 
       ownerWindow.PanelUI.showSubView(aWidget.viewId, anchor, aEvent);
     }
@@ -1799,17 +1799,17 @@ var CustomizableUIInternal = {
       target = target.parentNode;
     }
     if (closemenu == "none" || widgetType == "view") {
       return;
     }
 
     if (closemenu == "single") {
       let panel = this._getPanelForNode(target);
-      let multiview = panel.querySelector("photonpanelmultiview,panelmultiview");
+      let multiview = panel.querySelector("panelmultiview");
       if (multiview.showingSubView) {
         if (multiview.instance.panelViews) {
           multiview.goBack();
         } else {
           multiview.showMainView();
         }
         return;
       }
@@ -4298,25 +4298,20 @@ OverflowableToolbar.prototype = {
 
   show(aEvent) {
     if (this._panel.state == "open") {
       return Promise.resolve();
     }
     return new Promise(resolve => {
       let doc = this._panel.ownerDocument;
       this._panel.hidden = false;
-      let photonView = this._panel.querySelector("photonpanelmultiview");
-      let contextMenu;
-      if (photonView) {
-        let mainViewId = photonView.getAttribute("mainViewId");
-        let mainView = doc.getElementById(mainViewId);
-        contextMenu = doc.getElementById(mainView.getAttribute("context"));
-      } else {
-        contextMenu = doc.getElementById(this._panel.getAttribute("context"));
-      }
+      let multiview = this._panel.querySelector("panelmultiview");
+      let mainViewId = multiview.getAttribute("mainViewId");
+      let mainView = doc.getElementById(mainViewId);
+      let contextMenu = doc.getElementById(mainView.getAttribute("context"));
       gELS.addSystemEventListener(contextMenu, "command", this, true);
       let anchor = doc.getAnonymousElementByAttribute(this._chevron, "class", "toolbarbutton-icon");
       // Ensure we update the gEditUIVisible flag when opening the popup, in
       // case the edit controls are in it.
       this._panel.addEventListener("popupshowing", () => doc.defaultView.updateEditUIVisibility(), {once: true});
       this._panel.openPopup(anchor || this._chevron, { triggerEvent: aEvent });
       this._chevron.open = true;
 

--- a/browser/components/customizableui/content/panelUI.css
+++ b/browser/components/customizableui/content/panelUI.css
@@ -2,41 +2,34 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 .panel-viewcontainer {
   overflow: hidden;
 }
 
 .panel-viewstack {
+  overflow: visible;
   transition: height var(--panelui-subview-transition-duration);
 }
 
 .panel-viewcontainer[panelopen] {
   transition-property: height;
   transition-timing-function: var(--animation-easing-function);
   transition-duration: var(--panelui-subview-transition-duration);
   will-change: height;
 }
 
-/* START photon adjustments */
-
-photonpanelmultiview > .panel-viewcontainer > .panel-viewstack {
-  overflow: visible;
-}
-
-photonpanelmultiview[transitioning] {
+panelmultiview[transitioning] {
   pointer-events: none;
 }
 
 .panel-viewcontainer.offscreen {
   position: absolute;
   top: 100000px;
   left: 100000px;
 }
 
 .panel-viewcontainer.offscreen,
 .panel-viewcontainer.offscreen > .panel-viewstack {
   margin: 0;
   padding: 0;
 }
-
-/* END photon adjustments */

--- a/browser/components/customizableui/content/panelUI.inc.xul
+++ b/browser/components/customizableui/content/panelUI.inc.xul
@@ -4,32 +4,32 @@
 
 <panel id="widget-overflow"
        role="group"
        type="arrow"
        noautofocus="true"
        position="bottomcenter topright"
        photon="true"
        hidden="true">
-  <photonpanelmultiview mainViewId="widget-overflow-mainView" disablekeynav="true">
+  <panelmultiview mainViewId="widget-overflow-mainView" disablekeynav="true">
     <panelview id="widget-overflow-mainView"
                context="toolbar-context-menu">
       <vbox class="panel-subview-body">
         <vbox id="widget-overflow-list" class="widget-overflow-list"
               overflowfortoolbar="nav-bar"/>
         <toolbarseparator id="widget-overflow-fixed-separator" hidden="true"/>
         <vbox id="widget-overflow-fixed-list" class="widget-overflow-list" hidden="true" />
       </vbox>
       <toolbarbutton command="cmd_CustomizeToolbars"
                       id="overflowMenu-customize-button"
                       class="subviewbutton panel-subview-footer"
                       accesskey="&overflowCustomizeToolbar.accesskey;"
                       label="&overflowCustomizeToolbar.label;"/>
     </panelview>
-  </photonpanelmultiview>
+  </panelmultiview>
   <!-- This menu is here because not having it in the menu in which it's used flickers
        when hover styles overlap. See https://bugzilla.mozilla.org/show_bug.cgi?id=1378427 .
        -->
   <menupopup id="customizationPanelItemContextMenu"
              onpopupshowing="gCustomizeMode.onPanelContextMenuShowing(event)">
     <menuitem oncommand="gCustomizeMode.addToPanel(document.popupNode)"
               id="customizationPanelItemContextMenuPin"
               accesskey="&customizeMenu.pinToOverflowMenu.accesskey;"
@@ -159,18 +159,18 @@
 <panel id="appMenu-popup"
        class="cui-widget-panel"
        role="group"
        type="arrow"
        hidden="true"
        flip="slide"
        position="bottomcenter topright"
        noautofocus="true">
-  <photonpanelmultiview id="appMenu-multiView" mainViewId="appMenu-mainView"
-                        viewCacheId="appMenu-viewCache">
+  <panelmultiview id="appMenu-multiView" mainViewId="appMenu-mainView"
+                  viewCacheId="appMenu-viewCache">
     <panelview id="appMenu-mainView" class="PanelUI-subView"
                descriptionheightworkaround="true">
       <vbox class="panel-subview-body">
         <vbox id="appMenu-addon-banners"/>
         <toolbarbutton class="panel-banner-item"
                        label-update-available="&updateAvailable.panelUI.label;"
                        label-update-manual="&updateManual.panelUI.label;"
                        label-update-restart="&updateRestart.panelUI.label2;"
@@ -662,17 +662,17 @@
                        placesanonid="view-toolbar"
                        toolbarId="PersonalToolbar"
                        type="checkbox"
                        oncommand="onViewToolbarCommand(event)"
                        label="&viewBookmarksToolbar.label;"
                        label-checked="&hideBookmarksToolbar.label;"/>
       </vbox>
     </panelview>
-  </photonpanelmultiview>
+  </panelmultiview>
 </panel>
 
 <panel id="downloads-button-autohide-panel"
        role="group"
        type="arrow"
        hidden="true"
        onpopupshown="gCustomizeMode._downloadPanelAutoHideTimeout = setTimeout(() => event.target.hidePopup(), 4000);"
        onmouseover="clearTimeout(gCustomizeMode._downloadPanelAutoHideTimeout);"

--- a/browser/components/customizableui/content/panelUI.js
+++ b/browser/components/customizableui/content/panelUI.js
@@ -394,17 +394,17 @@ const PanelUI = {
 
     if (!aAnchor) {
       Cu.reportError("Expected an anchor when opening subview with id: " + aViewId);
       return;
     }
 
     this.ensureLibraryInitialized(viewNode);
 
-    let container = aAnchor.closest("panelmultiview,photonpanelmultiview");
+    let container = aAnchor.closest("panelmultiview");
     if (container) {
       container.showSubView(aViewId, aAnchor);
     } else if (!aAnchor.open) {
       aAnchor.open = true;
 
       let tempPanel = document.createElement("panel");
       tempPanel.setAttribute("type", "arrow");
       tempPanel.setAttribute("id", "customizationui-widget-panel");
@@ -429,17 +429,17 @@ const PanelUI = {
       if (oldMultiView && oldMultiView.current == viewNode) {
         await oldMultiView.showMainView();
       }
 
       let viewShown = false;
       let listener = () => viewShown = true;
       viewNode.addEventListener("ViewShown", listener, {once: true});
 
-      let multiView = document.createElement("photonpanelmultiview");
+      let multiView = document.createElement("panelmultiview");
       multiView.setAttribute("id", "customizationui-widget-multiview");
       multiView.setAttribute("viewCacheId", "appMenu-viewCache");
       multiView.setAttribute("mainViewId", viewNode.id);
       multiView.setAttribute("ephemeral", true);
       document.getElementById("appMenu-viewCache").appendChild(viewNode);
       tempPanel.appendChild(multiView);
       viewNode.classList.add("cui-widget-panelview");
 

--- a/browser/components/customizableui/content/panelUI.xml
+++ b/browser/components/customizableui/content/panelUI.xml
@@ -13,47 +13,37 @@
           xmlns:xul="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
           xmlns:xbl="http://www.mozilla.org/xbl">
 
   <binding id="panelmultiview">
     <resources>
       <stylesheet src="chrome://browser/content/customizableui/panelUI.css"/>
     </resources>
     <content>
-      <xul:vbox anonid="viewContainer" class="panel-viewcontainer" xbl:inherits="panelopen,transitioning">
-        <xul:stack anonid="viewStack" xbl:inherits="transitioning" class="panel-viewstack">
+      <xul:box anonid="viewContainer" class="panel-viewcontainer" xbl:inherits="panelopen,transitioning">
+        <xul:box anonid="viewStack" xbl:inherits="transitioning" class="panel-viewstack">
           <children includes="panelview"/>
-        </xul:stack>
-      </xul:vbox>
+        </xul:box>
+      </xul:box>
+      <xul:box class="panel-viewcontainer offscreen">
+        <xul:box anonid="offscreenViewStack" class="panel-viewstack"/>
+      </xul:box>
     </content>
     <implementation>
       <constructor><![CDATA[
         const {PanelMultiView} = Components.utils.import("resource:///modules/PanelMultiView.jsm", {});
         this.instance = new PanelMultiView(this);
       ]]></constructor>
 
       <destructor><![CDATA[
         this.instance.destructor();
       ]]></destructor>
     </implementation>
   </binding>
 
-  <binding id="photonpanelmultiview" extends="chrome://browser/content/customizableui/panelUI.xml#panelmultiview">
-    <content>
-      <xul:box anonid="viewContainer" class="panel-viewcontainer" xbl:inherits="panelopen,transitioning">
-        <xul:box anonid="viewStack" xbl:inherits="transitioning" class="panel-viewstack">
-          <children includes="panelview"/>
-        </xul:box>
-      </xul:box>
-      <xul:box class="panel-viewcontainer offscreen">
-        <xul:box anonid="offscreenViewStack" class="panel-viewstack"/>
-      </xul:box>
-    </content>
-  </binding>
-
   <binding id="panelview">
     <content>
       <xul:box class="panel-header" anonid="header">
         <xul:toolbarbutton anonid="back"
                            class="subviewbutton subviewbutton-iconic subviewbutton-back"
                            closemenu="none"
                            tabindex="0"
                            tooltip="&backCmd.label;"

--- a/browser/components/customizableui/test/browser_overflow_use_subviews.js
+++ b/browser/components/customizableui/test/browser_overflow_use_subviews.js
@@ -34,17 +34,17 @@ add_task(async function check_developer_
   chevron.click();
   await shownPanelPromise;
 
   let developerView = document.getElementById("PanelUI-developer");
   let button = document.getElementById("developer-button");
   let subviewShownPromise = subviewShown(developerView);
   button.click();
   await subviewShownPromise;
-  let hasSubviews = !!kOverflowPanel.querySelector("photonpanelmultiview,panelmultiview");
+  let hasSubviews = !!kOverflowPanel.querySelector("panelmultiview");
   let expectedPanel = hasSubviews ? kOverflowPanel : document.getElementById("customizationui-widget-panel");
   is(developerView.closest("panel"), expectedPanel, "Should be inside the panel");
   expectedPanel.hidePopup();
   await Promise.resolve(); // wait for popup to hide fully.
   await stopOverflowing();
 });
 
 /**

--- a/browser/components/downloads/content/downloadsOverlay.xul
+++ b/browser/components/downloads/content/downloadsOverlay.xul
@@ -104,18 +104,18 @@
         <menuitem command="downloadsCmd_clearList"
                   label="&cmd.clearList2.label;"
                   accesskey="&cmd.clearList2.accesskey;"/>
         <menuitem command="downloadsCmd_clearDownloads"
                   hidden="true"
                   label="&cmd.clearDownloads.label;"/>
       </menupopup>
 
-      <photonpanelmultiview id="downloadsPanel-multiView"
-                            mainViewId="downloadsPanel-mainView">
+      <panelmultiview id="downloadsPanel-multiView"
+                      mainViewId="downloadsPanel-mainView">
 
         <panelview id="downloadsPanel-mainView">
           <vbox class="panel-view-body-unscrollable">
             <richlistbox id="downloadsListBox"
                          context="downloadsContextMenu"
                          onmouseover="DownloadsView.onDownloadMouseOver(event);"
                          onmouseout="DownloadsView.onDownloadMouseOut(event);"
                          oncontextmenu="DownloadsView.onDownloadContextMenu(event);"
@@ -202,13 +202,13 @@
             </toolbaritem>
           </vbox>
           <toolbarbutton id="PanelUI-downloadsMore"
                          class="panel-subview-footer subviewbutton"
                          label="&downloadsHistory.label;"
                          oncommand="BrowserDownloadsUI(); CustomizableUI.hidePanelForNode(this);"/>
         </panelview>
 
-      </photonpanelmultiview>
+      </panelmultiview>
 
     </panel>
   </popupset>
 </overlay>

--- a/browser/themes/osx/customizableui/panelUI.css
+++ b/browser/themes/osx/customizableui/panelUI.css
@@ -11,17 +11,17 @@
 .subviewbutton {
   padding-inline-start: 18px;
 }
 
 .subviewbutton.download {
   padding-inline-start: 14px;
 }
 
-photonpanelmultiview .toolbaritem-combined-buttons > spacer {
+panelmultiview .toolbaritem-combined-buttons > spacer {
   width: 42px; /* 18px toolbarbutton padding + 16px icon + 8px label padding start */
 }
 
 #appMenu-addon-banners > .addon-banner-item,
 #appMenu-mainView > .panel-subview-body > .panel-banner-item {
   padding-inline-start: 18px;
 }
 

--- a/browser/themes/shared/customizableui/panelUI.inc.css
+++ b/browser/themes/shared/customizableui/panelUI.inc.css
@@ -111,16 +111,18 @@
 #PanelUI-menu-button[badge-status="addon-alert"] > .toolbarbutton-badge-stack > .toolbarbutton-badge {
   height: 13px;
   background: #FFBF00 url(chrome://browser/skin/update-badge-failed.svg) no-repeat center;
 }
 
 panelview {
   -moz-box-orient: vertical;
   -moz-box-flex: 1;
+  background: var(--arrowpanel-background);
+  padding: 0;
 }
 
 /* This section is to anchor all the drop down panels at the same height, shift the
   panel`s top margin according to its positioning and the uidensity of the window. */
 #downloadsPanel,
 #widget-overflow,
 #appMenu-popup,
 #customizationui-widget-panel {
@@ -177,16 +179,17 @@ panelview {
 :root[uidensity=touch] #PersonalToolbar #BMB_bookmarksPopup {
   margin-top: -5px;
 }
 
 .panel-subview-body {
   overflow-y: auto;
   overflow-x: hidden;
   -moz-box-flex: 1;
+  padding: 6px 0;
 }
 
 .panel-view-body-unscrollable {
   overflow: hidden;
   -moz-box-flex: 1;
 }
 
 .subviewbutton.panel-subview-footer {
@@ -318,28 +321,21 @@ panelview:not([mainview]) .toolbarbutton
   text-align: start;
   display: -moz-box;
 }
 
 .cui-widget-panel > .panel-arrowcontainer > .panel-arrowcontent {
   padding: 4px 0;
 }
 
-/* START photonpanelview adjustments */
-
 #appMenu-popup > .panel-arrowcontainer > .panel-arrowcontent,
 panel[photon] > .panel-arrowcontainer > .panel-arrowcontent {
   padding: 0;
 }
 
-photonpanelmultiview panelview {
-  background: var(--arrowpanel-background);
-  padding: 0;
-}
-
 #appMenu-popup panelview,
 #customizationui-widget-multiview panelview:not([extension]) {
   min-width: @menuPanelWidth@;
   max-width: 35em;
 }
 
 #customizationui-widget-multiview #appMenu-libraryView,
 #pageActionPanel panelview,
@@ -348,22 +344,16 @@ photonpanelmultiview panelview {
   max-width: @wideMenuPanelWidth@;
 }
 
 /* Add 2 * 16px extra width for touch mode button padding. */
 #appMenu-popup[touchmode] panelview {
   min-width: calc(@menuPanelWidth@ + 32px);
 }
 
-photonpanelmultiview .panel-subview-body {
-  padding: 6px 0;
-}
-
-/* END photonpanelview adjustments */
-
 .cui-widget-panel.cui-widget-panelWithFooter > .panel-arrowcontainer > .panel-arrowcontent {
   padding-bottom: 0;
 }
 
 .toolbaritem-combined-buttons@inAnyPanel@ > toolbarbutton > .toolbarbutton-icon {
   min-width: 0;
   min-height: 0;
   margin: 0;
@@ -432,17 +422,18 @@ toolbarbutton[constrain-size="true"][cui
   display: none;
 }
 
 .addon-banner-item::after,
 .panel-banner-item::after {
   content: "";
   width: 16px;
   height: 16px;
-  margin-inline-end: 16.5px;
+  margin-inline-start: 10px;
+  margin-inline-end: 12px;
   display: -moz-box;
 }
 
 .addon-banner-item {
   background-color: var(--appmenu-yellow-warning-color);
   /* Force border to override `.addon-banner-item` selector below */
   border-top: 1px solid var(--appmenu-yellow-warning-border-color) !important;
   display: flex;
@@ -875,61 +866,45 @@ panelview .toolbarbutton-1,
 }
 
 /* This is a <label> but it should fit in with the menu font- and colorwise. */
 #PanelUI-characterEncodingView-autodetect-label {
   font: menu;
   color: inherit;
 }
 
-/* START photon adjustments */
-
 .subviewbutton[checked="true"] {
-  background: url(chrome://browser/skin/check.svg) center left 7px / 11px 11px no-repeat transparent;
+  list-style-image: url(chrome://browser/skin/check.svg);
   fill: currentColor;
 }
 
-.subviewbutton[checked="true"]:-moz-locale-dir(rtl) {
-  background-position: center right 7px;
-}
-
-photonpanelmultiview .subviewbutton[checked="true"] {
-  background: none;
-  list-style-image: url(chrome://browser/skin/check.svg);
-}
-
-photonpanelmultiview .subviewbutton > .menu-iconic-left {
-  -moz-appearance: none;
-  margin-inline-end: 0;
-}
-
 #appMenu-popup .toolbaritem-combined-buttons {
   -moz-box-align: center;
   -moz-box-orient: horizontal;
   border: 0;
   border-radius: 0;
   margin-inline-end: 8px;
 }
 
-photonpanelmultiview .toolbaritem-combined-buttons > label {
+panelmultiview .toolbaritem-combined-buttons > label {
   -moz-box-flex: 1;
   font: menu;
   margin: 0;
 }
 
-photonpanelmultiview .toolbaritem-combined-buttons > spacer.before-label {
+panelmultiview .toolbaritem-combined-buttons > spacer.before-label {
   width: 36px; /* 12px toolbarbutton padding + 16px icon + 8px label padding start */
 }
 
-photonpanelmultiview .toolbaritem-combined-buttons > spacer.after-label {
+panelmultiview .toolbaritem-combined-buttons > spacer.after-label {
   -moz-box-flex: 1;
   width: 20px; /* a little bigger than the width of the scrollbar */
 }
 
-photonpanelmultiview .PanelUI-subView .toolbaritem-combined-buttons > .subviewbutton {
+.PanelUI-subView .toolbaritem-combined-buttons > .subviewbutton {
   -moz-box-flex: 0;
   height: auto;
   margin-inline-start: 18px;
   min-width: auto;
   padding: 4px;
 }
 
 #appMenu-zoom-controls > .subviewbutton {
@@ -946,54 +921,43 @@ photonpanelmultiview .PanelUI-subView .t
   text-align: center;
 }
 
 .toolbaritem-combined-buttons > toolbarseparator[orient="vertical"] + .subviewbutton,
 #appMenu-zoom-controls > toolbarseparator[orient="vertical"] + .subviewbutton {
   margin-inline-start: 0;
 }
 
-photonpanelmultiview .PanelUI-subView .toolbaritem-combined-buttons >
-  .subviewbutton-iconic > .toolbarbutton-text,
-photonpanelmultiview .PanelUI-subView .toolbaritem-combined-buttons >
-  .subviewbutton:not(.subviewbutton-iconic) > .toolbarbutton-icon {
+.PanelUI-subView .toolbaritem-combined-buttons > .subviewbutton-iconic > .toolbarbutton-text,
+.PanelUI-subView .toolbaritem-combined-buttons > .subviewbutton:not(.subviewbutton-iconic) > .toolbarbutton-icon {
   display: none;
 }
 
 /* Using this selector, because this way the hover and active selectors will apply properly. */
-photonpanelmultiview .PanelUI-subView .toolbaritem-combined-buttons >
-  .subviewbutton:not(.subviewbutton-iconic) {
+.PanelUI-subView .toolbaritem-combined-buttons > .subviewbutton:not(.subviewbutton-iconic) {
   background-color: #f9f9f9;
   border: 1px solid #e1e1e1;
   border-radius: 10000px;
   padding: 1px 8px;
 }
 
-photonpanelmultiview .toolbaritem-combined-buttons > .subviewbutton:not(.subviewbutton-iconic) > .toolbarbutton-text {
+.toolbaritem-combined-buttons > .subviewbutton:not(.subviewbutton-iconic) > .toolbarbutton-text {
   font-size: 1em;
   padding-inline-start: 0;
 }
 
-photonpanelmultiview .addon-banner-item::after,
-photonpanelmultiview .panel-banner-item::after {
-  margin-inline-end: 12px;
-  margin-inline-start: 10px;
-}
-
-photonpanelmultiview .subview-subheader {
+.subview-subheader {
   color: GrayText;
 }
 
-photonpanelmultiview .subview-subheader,
-photonpanelmultiview .panel-subview-footer {
+.subview-subheader,
+.panel-subview-footer {
   font: menu;
 }
 
-/* END photon adjustments */
-
 panelview .toolbarbutton-1 {
   margin-top: 6px;
 }
 
 panelview .toolbarbutton-1@buttonStateHover@,
 toolbarbutton.subviewbutton@buttonStateHover@,
 menu.subviewbutton@menuStateHover@,
 menuitem.subviewbutton@menuStateHover@,
@@ -1079,22 +1043,26 @@ menuitem.panel-subview-footer@menuStateA
   -moz-appearance: none;
   min-height: 0;
   border-top: 1px solid var(--panel-separator-color);
   border-bottom: none;
   margin: 6px 0;
   padding: 0;
 }
 
-.PanelUI-subView menuseparator,
-.PanelUI-subView toolbarseparator {
+.PanelUI-subView menuseparator {
   margin-inline-start: -5px;
   margin-inline-end: -4px;
 }
 
+.PanelUI-subView toolbarseparator {
+  margin-inline-start: 0;
+  margin-inline-end: 0;
+}
+
 .PanelUI-subView menuseparator.small-separator,
 .PanelUI-subView toolbarseparator.small-separator {
   margin-left: 5px;
   margin-right: 5px;
 }
 
 .cui-widget-panelview menuseparator.small-separator {
   margin-left: 10px;
@@ -1211,17 +1179,16 @@ toolbarpaletteitem[place=panel] > .toolb
 .toolbaritem-combined-buttons@inAnyPanel@:hover > separator {
   margin: 0;
 }
 
 #widget-overflow > .panel-arrowcontainer > .panel-arrowcontent {
   padding: 0;
 }
 
-.cui-widget-panelview,
 #widget-overflow-mainView .panel-subview-body {
   overflow-y: auto;
   overflow-x: hidden;
 }
 
 .widget-overflow-list {
   width: @wideMenuPanelWidth@;
 }
@@ -1264,17 +1231,17 @@ toolbarpaletteitem[place=panel] > .subvi
 
 .widget-overflow-list .toolbarbutton-1:not(.toolbarbutton-combined) > .toolbarbutton-text {
   text-align: start;
   padding-inline-start: .5em;
 }
 
 .subviewbutton > .menu-iconic-left {
   -moz-appearance: none;
-  margin-inline-end: 3px;
+  margin-inline-end: 0;
 }
 
 menuitem[checked="true"].subviewbutton > .menu-iconic-left {
   visibility: hidden;
 }
 
 #PanelUI-panicView > .panel-subview-body,
 #PanelUI-panicView {
@@ -1463,18 +1430,16 @@ menuitem[checked="true"].subviewbutton >
     background-image: -moz-image-rect(url(chrome://browser/skin/panic-panel/icons@2x.png), 0, 96, 32, 64);
   }
 
   #PanelUI-panic-actionlist-newwindow {
     background-image: -moz-image-rect(url(chrome://browser/skin/panic-panel/icons@2x.png), 0, 128, 32, 96);
   }
 }
 
-/* START photon adjustments */
-
 .panel-header {
   align-items: center;
   border-bottom: 1px solid var(--panel-separator-color);
   display: flex;
   flex: 1 auto;
   height: 40px; /* fixed item height to prevent flex sizing; height + 2*4px padding */
   padding: 4px;
 }
@@ -1484,45 +1449,34 @@ menuitem[checked="true"].subviewbutton >
   font-size: 13px;
   font-weight: 500;
   margin: 0;
   /* Add the size of the back button to center properly. */
   margin-inline-end: 32px;
   text-align: center;
 }
 
-photonpanelmultiview .PanelUI-subView .panel-header > .subviewbutton-back {
+.PanelUI-subView .panel-header > .subviewbutton-back {
   -moz-context-properties: fill;
   fill: var(--arrowpanel-color);
   list-style-image: url(chrome://browser/skin/arrow-left.svg);
   padding: 8px;
 }
 
 .panel-header > .subviewbutton-back:-moz-locale-dir(rtl) {
   transform: scaleX(-1);
 }
 
 .panel-header > .subviewbutton-back > .toolbarbutton-text {
   /* !important to override .cui-widget-panel toolbarbutton:not([wrap]) > .toolbarbutton-text
    * selector further down. */
   display: none !important;
 }
 
-photonpanelmultiview .PanelUI-subView toolbarseparator {
-  margin-inline-start: 0;
-  margin-inline-end: 0;
-}
-
-/* This is explicitly overriding the overflow properties set above. */
-photonpanelmultiview .cui-widget-panelview {
-  overflow-x: visible;
-  overflow-y: visible;
-}
-
-photonpanelmultiview #panelMenu_pocket {
+#panelMenu_pocket {
   display: none;
 }
 
 .subviewbutton.download {
   -moz-box-align: start;
   min-height: 48px;
   padding-inline-start: 8px;
 }
@@ -1567,10 +1521,8 @@ photonpanelmultiview #panelMenu_pocket {
 
 .subviewbutton.download:-moz-any([openLabel],[retryLabel]) > .action-button@buttonStateHover@ {
   background-color: var(--arrowpanel-dimmed-further);
 }
 
 .subviewbutton.download:-moz-any([openLabel],[retryLabel]) > .action-button@buttonStateActive@ {
   background-color: var(--arrowpanel-dimmed-even-further);
 }
-
-/* END photon adjustments */