Add fail safe mechanism to Extension Event Router.

To investigate a crash on ChromeOS, fail safe code and reporting are
added to EventRouter dispatcher and ChromeExtensionsBrowserClient.

Bug: 870838
Change-Id: I8da1a56f80e247d68f26c8d8027f1eb36cea272f
Reviewed-on: https://chromium-review.googlesource.com/c/1335594
Commit-Queue: Ramin Halavati <rhalavati@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608434}

chrome/browser/extensions/chrome_extensions_browser_client.cc

@@ -114,6 +114,17 @@ bool ChromeExtensionsBrowserClient::AreExtensionsDisabled(
 
 bool ChromeExtensionsBrowserClient::IsValidContext(
     content::BrowserContext* context) {
+  // TODO(https://crbug.com/870838): Remove after investigating the bug.
+  if (!context) {
+    LOG(ERROR) << "Unexpected null context";
+    NOTREACHED();
+    return false;
+  }
+  if (!g_browser_process) {
+    LOG(ERROR) << "Unexpected null g_browser_process";
+    NOTREACHED();
+    return false;
+  }
   Profile* profile = static_cast<Profile*>(context);
   return g_browser_process->profile_manager() &&
          g_browser_process->profile_manager()->IsValidProfile(profile);

extensions/browser/event_router.cc

@@ -722,6 +722,12 @@ void EventRouter::DoDispatchEventToSenderBookkeepingOnUI(
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   BrowserContext* browser_context =
       reinterpret_cast<BrowserContext*>(browser_context_id);
+  // TODO(https://crbug.com/870838): Remove after investigating the bug.
+  if (!ExtensionsBrowserClient::Get()) {
+    LOG(ERROR) << "ExtensionsBrowserClient does not exist.";
+    NOTREACHED();
+    return;
+  }
   if (!ExtensionsBrowserClient::Get()->IsValidContext(browser_context))
     return;
   const Extension* extension =