Bug 1569060 - Add layout debugger command to dump process IDs. r=Gijs

Differential Revision: https://phabricator.services.mozilla.com/D39437

--HG--
extra : moz-landing-system : lando

browser/base/content/tabbrowser.js

@@ -4779,29 +4779,20 @@
         label = tab._fullLabel || tab.getAttribute("label");
       }
       if (AppConstants.NIGHTLY_BUILD) {
-        if (
-          tab.linkedBrowser &&
-          tab.linkedBrowser.isRemoteBrowser &&
-          tab.linkedBrowser.frameLoader
-        ) {
-          label +=
-            " (pid " + tab.linkedBrowser.frameLoader.remoteTab.osPid + ")";
-
-          // If we're running with fission enabled, try to include PID
-          // information for every remote subframe.
+        if (tab.linkedBrowser) {
+          // On Nightly builds, show the PID of the content process, and if
+          // we're running with fission enabled, try to include PIDs for
+          // every remote subframe.
+          let [contentPid, ...framePids] = E10SUtils.getBrowserPids(
+            tab.linkedBrowser,
+            gFissionBrowser
+          );
+          if (contentPid) {
+            label += " (pid " + contentPid + ")";
             if (gFissionBrowser) {
-            let pids = new Set();
-            let stack = [tab.linkedBrowser.browsingContext];
-            while (stack.length) {
-              let bc = stack.pop();
-              stack.push(...bc.getChildren());
-              if (bc.currentWindowGlobal) {
-                pids.add(bc.currentWindowGlobal.osPid);
+              label += " [F " + framePids.join(", ") + "]";
             }
           }
-
-            label += " [F " + Array.from(pids).join(", ") + "]";
-          }
         }
       }
       if (tab.userContextId) {

layout/tools/layout-debug/ui/content/layoutdebug.js

@@ -74,6 +74,20 @@ class Debugger {
     this._attached = true;
   }
 
+  dumpProcessIDs() {
+    let parentPid = Services.appinfo.processID;
+    let [contentPid, ...framePids] = E10SUtils.getBrowserPids(
+      gBrowser,
+      gFissionBrowser
+    );
+
+    dump(`Parent pid: ${parentPid}\n`);
+    dump(`Content pid: ${contentPid || "-"}\n`);
+    if (gFissionBrowser) {
+      dump(`Subframe pids: ${framePids.length ? framePids.join(", ") : "-"}\n`);
+    }
+  }
+
   get visualDebugging() {
     return this._visualDebugging;
   }

layout/tools/layout-debug/ui/content/layoutdebug.xul

@@ -80,6 +80,7 @@
         <menu label="&ldb.DumpMenu.label;"
               accesskey="&ldb.DumpMenu.accesskey;">
           <menupopup>
+            <menuitem id="menu_processIDs" label="Process IDs" accesskey="P" oncommand="gDebugger.dumpProcessIDs();" />
             <menuitem id="menu_dumpWebShells" label="&ldb.dumpWebShells.label;" accesskey="&ldb.dumpWebShells.accesskey;" oncommand="gDebugger.dumpWebShells();" />
             <menuitem id="menu_dumpContent" label="&ldb.dumpContent.label;" accesskey="&ldb.dumpContent.accesskey;" oncommand="gDebugger.dumpContent();" />
             <menuitem id="menu_dumpFrames" label="&ldb.dumpFrames.label;" accesskey="&ldb.dumpFrames.accesskey;" oncommand="gDebugger.dumpFrames();" />

toolkit/modules/E10SUtils.jsm

@@ -774,6 +774,31 @@ var E10SUtils = {
     }
     return deserialized;
   },
+
+  /**
+   * Returns the pids for a remote browser and its remote subframes.
+   */
+  getBrowserPids(aBrowser, aRemoteSubframes) {
+    if (!aBrowser.isRemoteBrowser || !aBrowser.frameLoader) {
+      return [];
+    }
+    let tabPid = aBrowser.frameLoader.remoteTab.osPid;
+    let pids = new Set();
+    if (aRemoteSubframes) {
+      let stack = [aBrowser.browsingContext];
+      while (stack.length) {
+        let bc = stack.pop();
+        stack.push(...bc.getChildren());
+        if (bc.currentWindowGlobal) {
+          let pid = bc.currentWindowGlobal.osPid;
+          if (pid != tabPid) {
+            pids.add(pid);
+          }
+        }
+      }
+    }
+    return [tabPid, ...pids];
+  },
 };
 
 XPCOMUtils.defineLazyGetter(