Bug 1768209 - [devtools] Fix Disable Popup Auto-Hide + Browser Toolbox highlighters. r=emilio.

Using insertAnonymousContent on a document where a XUL popup is displayed seems
to hide/destroy it.
This patch extends the current behaviour for XUL windows to Chrome windows:
we add an iframe in the document which will contain the anonymous content.

Differential Revision: https://phabricator.services.mozilla.com/D146036

devtools/server/actors/highlighters/utils/markup.js

@@ -266,17 +266,21 @@ CanvasFrameAnonymousContentHelper.prototype = {
       // CanvasFrameAnonymousContentHelper was already destroyed.
       return;
     }
-    if (isXUL(this.highlighterEnv.window)) {
+
+    const window = this.highlighterEnv.window;
+    const isXULWindow = isXUL(window);
+    const isChromeWindow = window.isChromeWindow;
+
+    if (isXULWindow || isChromeWindow) {
       // In order to use anonymous content, we need to create and use an IFRAME
       // inside a XUL document first and use its window/document the same way we
-      // would normally use highlighter environment's window/document. See
-      // TODO: bug 1594587 for more details.
-      //
-      // Note: xul:window is not necessarily the top chrome window (as it's the
-      // case with about:devtools-toolbox). We need to ensure that we use the
-      // top chrome window to look up or create the iframe.
+      // would normally use highlighter environment's window/document.
+      // See Bug 1594587 for more details.
+      // For Chrome Windows, we also need to do it as the first call to insertAnonymousContent
+      // closes XUL popups even if ui.popup.disable_autohide is true (See Bug 1768896).
+
+      const { documentElement } = window.document;
       if (!this._iframe) {
-        const { documentElement } = this.highlighterEnv.window.document;
         this._iframe = documentElement.querySelector(
           ":scope > .devtools-highlighter-renderer"
         );
@@ -286,19 +290,19 @@ CanvasFrameAnonymousContentHelper.prototype = {
           const numberOfHighlighters =
             parseInt(this._iframe.dataset.numberOfHighlighters, 10) + 1;
           this._iframe.dataset.numberOfHighlighters = numberOfHighlighters;
-        } else {
-          this._iframe = this.highlighterEnv.window.document.createElement(
-            "iframe"
-          );
-          this._iframe.classList.add("devtools-highlighter-renderer");
-          // If iframe is used for the first time, add ref count of one to its
-          // numberOfHighlighters data attribute.
-          this._iframe.dataset.numberOfHighlighters = 1;
-          documentElement.append(this._iframe);
-          loadSheet(this.highlighterEnv.window, XUL_HIGHLIGHTER_STYLES_SHEET);
         }
       }
 
+      if (!this._iframe) {
+        this._iframe = window.document.createElement("iframe");
+        this._iframe.classList.add("devtools-highlighter-renderer");
+        // If iframe is used for the first time, add ref count of one to its
+        // numberOfHighlighters data attribute.
+        this._iframe.dataset.numberOfHighlighters = 1;
+        documentElement.append(this._iframe);
+        loadSheet(window, XUL_HIGHLIGHTER_STYLES_SHEET);
+      }
+
       if (this.waitForDocumentToLoad) {
         await waitForContentLoaded(this._iframe);
       }