Bug 1892905 - [devtools] Ensure tracing DOM Events for same-process iframe. r=devtools-reviewers,nchevobbe

The previous patch explicitly prevents spawning JavaScriptTracer for same-process iframe,
as the JavaScriptTracer can only be spawn once per thread.
But then the JavaScriptTracer should ensure tracking DOM Events for these same-process iframe globals.
`DebuggerNotificationObserver` requires to connect to each individual WindowGlobal.
Connecting to the top WindowGlobal isn't enough to receive DOM Events for children WindowGlobals.

Differential Revision: https://phabricator.services.mozilla.com/D208468

devtools/client/debugger/test/mochitest/browser_dbg-javascript-tracer.js

@@ -12,6 +12,19 @@ add_task(async function () {
 
   const dbg = await initDebugger("doc-scripts.html");
 
+  // Add an iframe before starting the tracer to later check for key event on it
+  const preExistingIframeBrowsingContext = await SpecialPowers.spawn(
+    gBrowser.selectedBrowser,
+    [],
+    async function () {
+      const iframe = content.document.createElement("iframe");
+      iframe.src = `data:text/html,<input type="text" value="pre existing iframe" onkeydown="console.log('keydown')" />`;
+      content.document.body.appendChild(iframe);
+      await new Promise(resolve => (iframe.onload = resolve));
+      return iframe.contentWindow.browsingContext;
+    }
+  );
+
   info("Enable the tracing");
   await clickElement(dbg, "trace");
 
@@ -55,6 +68,38 @@ add_task(async function () {
   await hasConsoleMessage(dbg, "DOM | click");
   await hasConsoleMessage(dbg, "λ simple");
 
+  const iframeBrowsingContext = await SpecialPowers.spawn(
+    gBrowser.selectedBrowser,
+    [],
+    async function () {
+      const iframe = content.document.createElement("iframe");
+      iframe.src = `data:text/html,<input type="text" value="new iframe" onkeypress="console.log('keypress')" />`;
+      content.document.body.appendChild(iframe);
+      await new Promise(resolve => (iframe.onload = resolve));
+      iframe.contentWindow.document.querySelector("input").focus();
+      return iframe.contentWindow.browsingContext;
+    }
+  );
+
+  await BrowserTestUtils.synthesizeKey("x", {}, iframeBrowsingContext);
+  await hasConsoleMessage(dbg, "DOM | keypress");
+  await hasConsoleMessage(dbg, "λ onkeypress");
+
+  await SpecialPowers.spawn(
+    preExistingIframeBrowsingContext,
+    [],
+    async function () {
+      content.document.querySelector("input").focus();
+    }
+  );
+  await BrowserTestUtils.synthesizeKey(
+    "x",
+    {},
+    preExistingIframeBrowsingContext
+  );
+  await hasConsoleMessage(dbg, "DOM | keydown");
+  await hasConsoleMessage(dbg, "λ onkeydown");
+
   // Test Blackboxing
   info("Clear the console from previous traces");
   const { hud } = await dbg.toolbox.getPanel("webconsole");

devtools/server/tracer/tracer.sys.mjs

@@ -312,6 +312,37 @@ class JavaScriptTracer {
     this.debuggerNotificationObserver.addListener(this.eventListener);
     this.debuggerNotificationObserver.connect(this.tracedGlobal);
 
+    // When we are tracing a document, also ensure connecting to all its children iframe globals.
+    // If we don't, Debugger API would fire onEnterFrame for their JavaScript code,
+    // but DOM Events wouldn't be notified by DebuggerNotificationObserver.
+    if (!isWorker && this.tracedGlobal instanceof Ci.nsIDOMWindow) {
+      const { browserId } = this.tracedGlobal.browsingContext;
+      // Keep track of any future global
+      this.dbg.onNewGlobalObject = g => {
+        try {
+          const win = g.unsafeDereference();
+          // only process globals relating to documents, and which are within the debugged tab
+          if (
+            win instanceof Ci.nsIDOMWindow &&
+            win.browsingContext.browserId == browserId
+          ) {
+            this.dbg.addDebuggee(g);
+            this.debuggerNotificationObserver.connect(win);
+          }
+        } catch (e) {}
+      };
+      // Register all, already existing children
+      for (const browsingContext of this.tracedGlobal.browsingContext.getAllBrowsingContextsInSubtree()) {
+        try {
+          // Only consider children which run in the same process, and exposes their window object
+          if (browsingContext.window) {
+            this.dbg.addDebuggee(browsingContext.window);
+            this.debuggerNotificationObserver.connect(browsingContext.window);
+          }
+        } catch (e) {}
+      }
+    }
+
     this.currentDOMEvent = null;
   }