--- a/devtools/client/shared/test/browser_html_tooltip-02.js
+++ b/devtools/client/shared/test/browser_html_tooltip-02.js
@@ -23,17 +23,16 @@ const TEST_URI = `data:text/xml;charset=
       <iframe id="frame" width="200"></iframe>
     </vbox>
   </window>`;
 
 const {HTMLTooltip} = require("devtools/client/shared/widgets/HTMLTooltip");
 loadHelperScript("helper_html_tooltip.js");
 
 add_task(function* () {
-  yield addTab("about:blank");
   let [,, doc] = yield createHost("bottom", TEST_URI);
 
   yield testClickInTooltipContent(doc);
   yield testConsumeOutsideClicksFalse(doc);
   yield testConsumeOutsideClicksTrue(doc);
   yield testClickInOuterIframe(doc);
   yield testClickInInnerIframe(doc);
 });

--- a/devtools/client/shared/test/browser_html_tooltip-03.js
+++ b/devtools/client/shared/test/browser_html_tooltip-03.js
@@ -27,17 +27,16 @@ const TEST_URI = `data:text/xml;charset=
       </hbox>
     </vbox>
   </window>`;
 
 const {HTMLTooltip} = require("devtools/client/shared/widgets/HTMLTooltip");
 loadHelperScript("helper_html_tooltip.js");
 
 add_task(function* () {
-  yield addTab("about:blank");
   let [, , doc] = yield createHost("bottom", TEST_URI);
 
   yield testNoAutoFocus(doc);
   yield testAutoFocus(doc);
   yield testAutoFocusPreservesFocusChange(doc);
 });
 
 function* testNoAutoFocus(doc) {

--- a/devtools/client/shared/test/browser_html_tooltip-04.js
+++ b/devtools/client/shared/test/browser_html_tooltip-04.js
@@ -31,17 +31,16 @@ loadHelperScript("helper_html_tooltip.js
 
 const TOOLTIP_HEIGHT = 30;
 const TOOLTIP_WIDTH = 100;
 
 add_task(function* () {
   // Force the toolbox to be 400px high;
   yield pushPref("devtools.toolbox.footer.height", 400);
 
-  yield addTab("about:blank");
   let [,, doc] = yield createHost("bottom", TEST_URI);
 
   info("Create HTML tooltip");
   let tooltip = new HTMLTooltip({doc}, {});
   let div = doc.createElementNS(HTML_NS, "div");
   div.style.height = "100%";
   tooltip.setContent(div, {width: TOOLTIP_WIDTH, height: TOOLTIP_HEIGHT});
 

--- a/devtools/client/shared/test/browser_html_tooltip-05.js
+++ b/devtools/client/shared/test/browser_html_tooltip-05.js
@@ -27,18 +27,16 @@ const {HTMLTooltip} = require("devtools/
 loadHelperScript("helper_html_tooltip.js");
 
 const TOOLTIP_HEIGHT = 200;
 const TOOLTIP_WIDTH = 200;
 
 add_task(function* () {
   // Force the toolbox to be 200px high;
   yield pushPref("devtools.toolbox.footer.height", 200);
-
-  yield addTab("about:blank");
   let [,, doc] = yield createHost("bottom", TEST_URI);
 
   info("Create HTML tooltip");
   let tooltip = new HTMLTooltip({doc}, {});
   let div = doc.createElementNS(HTML_NS, "div");
   div.style.height = "100%";
   tooltip.setContent(div, {width: TOOLTIP_WIDTH, height: TOOLTIP_HEIGHT});
 

--- a/devtools/client/shared/test/browser_html_tooltip_arrow-01.js
+++ b/devtools/client/shared/test/browser_html_tooltip_arrow-01.js
@@ -48,17 +48,16 @@ const TEST_URI = `data:text/xml;charset=
 
 const {HTMLTooltip} = require("devtools/client/shared/widgets/HTMLTooltip");
 loadHelperScript("helper_html_tooltip.js");
 
 add_task(function* () {
   // Force the toolbox to be 200px high;
   yield pushPref("devtools.toolbox.footer.height", 200);
 
-  yield addTab("about:blank");
   let [,, doc] = yield createHost("bottom", TEST_URI);
 
   info("Create HTML tooltip");
   let tooltip = new HTMLTooltip({doc}, {type: "arrow"});
   let div = doc.createElementNS(HTML_NS, "div");
   div.style.height = "35px";
   tooltip.setContent(div, {width: 200, height: 35});
 

--- a/devtools/client/shared/test/browser_html_tooltip_variable-height.js
+++ b/devtools/client/shared/test/browser_html_tooltip_variable-height.js
@@ -28,17 +28,16 @@ const TOOLTIP_HEIGHT = 50;
 
 const {HTMLTooltip} = require("devtools/client/shared/widgets/HTMLTooltip");
 loadHelperScript("helper_html_tooltip.js");
 
 add_task(function* () {
   // Force the toolbox to be 400px tall => 50px for each box.
   yield pushPref("devtools.toolbox.footer.height", 400);
 
-  yield addTab("about:blank");
   let [,, doc] = yield createHost("bottom", TEST_URI);
 
   let tooltip = new HTMLTooltip({doc}, {});
   info("Set tooltip content 50px tall, but request a container 200px tall");
   let tooltipContent = doc.createElementNS(HTML_NS, "div");
   tooltipContent.style.cssText = "height: " + TOOLTIP_HEIGHT + "px; background: red;";
   tooltip.setContent(tooltipContent, {width: CONTAINER_WIDTH, height: CONTAINER_HEIGHT});
 

--- a/devtools/client/shared/test/browser_html_tooltip_width-auto.js
+++ b/devtools/client/shared/test/browser_html_tooltip_width-auto.js
@@ -21,17 +21,16 @@ const TEST_URI = `data:text/xml;charset=
       <hbox id="box4" flex="1">test4</hbox>
     </vbox>
   </window>`;
 
 const {HTMLTooltip} = require("devtools/client/shared/widgets/HTMLTooltip");
 loadHelperScript("helper_html_tooltip.js");
 
 add_task(function* () {
-  yield addTab("about:blank");
   let [,, doc] = yield createHost("bottom", TEST_URI);
 
   let tooltip = new HTMLTooltip({doc}, {});
   info("Create tooltip content width to 150px");
   let tooltipContent = doc.createElementNS(HTML_NS, "div");
   tooltipContent.style.cssText = "height: 100%; width: 150px; background: red;";
 
   info("Set tooltip content using width:auto");

--- a/devtools/client/shared/test/browser_inplace-editor_autocomplete_01.js
+++ b/devtools/client/shared/test/browser_inplace-editor_autocomplete_01.js
@@ -38,33 +38,30 @@ const mockGetCSSPropertyList = function 
     "box-sizing",
     "color",
     "display",
     "visibility",
   ];
 };
 
 add_task(function* () {
-  yield addTab("data:text/html;charset=utf-8," +
-    "inplace editor CSS property autocomplete");
   let [host, win, doc] = yield createHost();
 
   let xulDocument = win.top.document;
   let popup = new AutocompletePopup(xulDocument, { autoSelect: true });
   yield new Promise(resolve => {
     createInplaceEditorAndClick({
       start: runPropertyAutocompletionTest,
       contentType: InplaceEditor.CONTENT_TYPES.CSS_PROPERTY,
       done: resolve,
       popup: popup
     }, doc);
   });
 
   host.destroy();
-  gBrowser.removeCurrentTab();
 });
 
 let runPropertyAutocompletionTest = Task.async(function* (editor) {
   info("Starting to test for css property completion");
   editor._getCSSPropertyList = mockGetCSSPropertyList;
 
   for (let data of testData) {
     yield testCompletion(data, editor);

--- a/devtools/client/shared/test/browser_inplace-editor_autocomplete_02.js
+++ b/devtools/client/shared/test/browser_inplace-editor_autocomplete_02.js
@@ -39,18 +39,16 @@ const mockGetCSSValuesForPropertyName = 
       "inline-block",
       "none",
     ]
   };
   return values[propertyName] || [];
 };
 
 add_task(function* () {
-  yield addTab("data:text/html;charset=utf-8," +
-    "inplace editor CSS value autocomplete");
   let [host, win, doc] = yield createHost();
 
   let xulDocument = win.top.document;
   let popup = new AutocompletePopup(xulDocument, { autoSelect: true });
 
   yield new Promise(resolve => {
     createInplaceEditorAndClick({
       start: runAutocompletionTest,
@@ -59,17 +57,16 @@ add_task(function* () {
         name: "display"
       },
       done: resolve,
       popup: popup
     }, doc);
   });
 
   host.destroy();
-  gBrowser.removeCurrentTab();
 });
 
 let runAutocompletionTest = Task.async(function* (editor) {
   info("Starting to test for css property completion");
   editor._getCSSValuesForPropertyName = mockGetCSSValuesForPropertyName;
 
   for (let data of testData) {
     yield testCompletion(data, editor);

--- a/devtools/client/shared/test/browser_inplace-editor_autocomplete_offset.js
+++ b/devtools/client/shared/test/browser_inplace-editor_autocomplete_offset.js
@@ -53,17 +53,16 @@ const mockGetCSSValuesForPropertyName = 
   let values = {
     "color": ["blue", "red"],
     "display": ["block", "flex", "none"]
   };
   return values[propertyName] || [];
 };
 
 add_task(function* () {
-  yield addTab("data:text/html;charset=utf-8,inplace editor CSS value autocomplete");
   let [host, win, doc] = yield createHost();
 
   let xulDocument = win.top.document;
   let popup = new AutocompletePopup(xulDocument, { autoSelect: true });
 
   info("Create a CSS_MIXED type autocomplete");
   yield new Promise(resolve => {
     createInplaceEditorAndClick({
@@ -71,17 +70,16 @@ add_task(function* () {
       start: runAutocompletionTest,
       contentType: InplaceEditor.CONTENT_TYPES.CSS_MIXED,
       done: resolve,
       popup: popup
     }, doc);
   });
 
   host.destroy();
-  gBrowser.removeCurrentTab();
 });
 
 let runAutocompletionTest = Task.async(function* (editor) {
   info("Starting autocomplete test for inplace-editor popup offset");
   editor._getCSSPropertyList = mockGetCSSPropertyList;
   editor._getCSSValuesForPropertyName = mockGetCSSValuesForPropertyName;
 
   let previousOffset = -1;