[Extensions Toolbar] Observe original profile for extension host notifications

Extension host closed notifications are sent from the original profile (never
the incognito profile). Use the original profile when listening for these
notifications.

BUG=454320

Review URL: https://codereview.chromium.org/898603002

Cr-Commit-Position: refs/heads/master@{#314360}

chrome/browser/ui/extensions/extension_action_view_controller.cc

@@ -288,7 +288,8 @@ bool ExtensionActionViewController::ShowPopupWithUrl(
   if (popup_host_) {
     // Lazily register for notifications about extension host destructions.
     static const int kType = extensions::NOTIFICATION_EXTENSION_HOST_DESTROYED;
-    content::Source<content::BrowserContext> source(browser_->profile());
+    content::Source<content::BrowserContext> source(
+        browser_->profile()->GetOriginalProfile());
     if (!registrar_.IsRegistered(this, kType, source))
       registrar_.Add(this, kType, source);