--- a/browser/themes/shared/toolbarbuttons.inc.css
+++ b/browser/themes/shared/toolbarbuttons.inc.css
@@ -119,18 +119,16 @@ toolbar .toolbarbutton-1 > menupopup.cui
 
 .findbar-button > .toolbarbutton-text,
 toolbarbutton.bookmark-item:not(.subviewbutton),
 toolbar .toolbarbutton-1 > .toolbarbutton-icon,
 toolbar .toolbarbutton-1 > .toolbarbutton-text,
 toolbar .toolbarbutton-1 > .toolbarbutton-badge-stack {
   padding: var(--toolbarbutton-inner-padding);
   border-radius: var(--toolbarbutton-border-radius);
-  transition-property: background-color, border-color, box-shadow;
-  transition-duration: var(--toolbarbutton-hover-transition-duration);
 }
 
 toolbar .toolbarbutton-1 > .toolbarbutton-icon {
   /* horizontal padding + actual icon width */
   width: calc(2 * var(--toolbarbutton-inner-padding) + 16px);
 }
 
 .bookmark-item > .toolbarbutton-menu-dropmarker,
@@ -223,16 +221,18 @@ toolbar .toolbarbutton-1[checked]:not(:a
 :root:not([uidensity=compact]) #back-button > .toolbarbutton-icon {
   background-color: var(--backbutton-background);
   background-origin: padding-box;
   background-clip: padding-box;
   border: 1px solid var(--backbutton-border-color);
   border-radius: 10000px;
   width: 32px;
   padding: 7px;
+  transition-property: box-shadow;
+  transition-duration: var(--toolbarbutton-hover-transition-duration);
 }
 
 :root[uidensity=touch] #back-button {
   padding-top: 1px;
   padding-bottom: 1px;
 }
 
 :root[uidensity=touch] #back-button > .toolbarbutton-icon {

--- a/browser/themes/shared/urlbar-searchbar.inc.css
+++ b/browser/themes/shared/urlbar-searchbar.inc.css
@@ -175,31 +175,24 @@
 
 :root[uidensity=touch] .urlbar-icon {
   width: 30px;
   height: 30px;
   /* 30x30 box - 16x16 image = 14x14 padding, 7 on each side */
   padding: 7px;
 }
 
-.urlbar-icon,
-.urlbar-icon-wrapper {
-  transition-property: background-color;
-  transition-duration: var(--toolbarbutton-hover-transition-duration);
-}
-
 .urlbar-icon:hover,
 .urlbar-icon-wrapper:hover {
   background-color: hsla(0,0%,80%,.4);
 }
 
 .urlbar-icon:hover:active,
 .urlbar-icon-wrapper:hover:active {
   background-color: hsla(0,0%,80%,.45);
-  transition-duration: var(--toolbarbutton-active-transition-duration);
 }
 
 .urlbar-icon-wrapper > .urlbar-icon:hover,
 .urlbar-icon-wrapper > .urlbar-icon:hover:active {
   background-color: transparent;
 }
 
 .urlbar-go-button,

--- a/toolkit/content/tests/browser/browser.ini
+++ b/toolkit/content/tests/browser/browser.ini
@@ -46,17 +46,17 @@ tags = audiochannel
 [browser_block_silentAudioTrack_media.js]
 tags = audiochannel
 [browser_block_webAudio.js]
 tags = audiochannel
 [browser_bug1170531.js]
 [browser_bug1198465.js]
 [browser_bug295977_autoscroll_overflow.js]
 [browser_bug451286.js]
-skip-if = !e10s
+skip-if = true # bug 1399845 tracks re-enabling this test.
 [browser_bug594509.js]
 [browser_bug982298.js]
 [browser_charsetMenu_swapBrowsers.js]
 [browser_content_url_annotation.js]
 skip-if = !e10s || !crashreporter
 [browser_contentTitle.js]
 [browser_crash_previous_frameloader.js]
 run-if = e10s && crashreporter