Added null checks for properties on ToolbarView that can be null.

BrowserView's toolbar() will have null app_menu_button() and
browser_actions() in hosted app windows, which could result in null
dereferences in certain corner cases. This adds null checks where it's
obviously safe to do so.

A better fix would be to use toolbar_button_provider() to access the
hosted app window's real app menu button and actions container, but that
requires more careful consideration.

Bug: 826596, 811982
Change-Id: Iea0a0ea3acffe5ed1016e61bd8ae2fe36971c79d
Reviewed-on: https://chromium-review.googlesource.com/1010002Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Commit-Queue: Matt Giuca <mgiuca@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550381}

chrome/browser/feature_engagement/incognito_window/incognito_window_tracker.cc

@@ -23,13 +23,13 @@ constexpr int kDefaultIncognitoWindowPromoShowTimeInHours = 2;
 constexpr char kIncognitoWindowObservedSessionTimeKey[] =
     "incognito_window_in_product_help_observed_session_time_key";
 
+// Note: May return null.
 BrowserAppMenuButton* GetAppMenuButton() {
   auto* browser = BrowserView::GetBrowserViewForBrowser(
       BrowserList::GetInstance()->GetLastActive());
   DCHECK(browser);
   DCHECK(browser->IsActive());
   DCHECK(browser->toolbar());
-  DCHECK(browser->toolbar()->app_menu_button());
   return browser->toolbar()->app_menu_button();
 }
 
@@ -53,7 +53,6 @@ void IncognitoWindowTracker::OnIncognitoWindowOpened() {
 
 void IncognitoWindowTracker::OnBrowsingDataCleared() {
   auto* app_menu_button = GetAppMenuButton();
-  // TODO(bdea): Remove early return once https://crbug.com/811982 is fixed.
   if (!app_menu_button)
     return;
 
@@ -87,7 +86,9 @@ void IncognitoWindowTracker::OnWidgetDestroying(views::Widget* widget) {
 
   if (incognito_promo_observer_.IsObserving(widget)) {
     incognito_promo_observer_.Remove(widget);
-    GetAppMenuButton()->SetIsProminent(false);
+    BrowserAppMenuButton* app_menu_button = GetAppMenuButton();
+    if (app_menu_button)
+      app_menu_button->SetIsProminent(false);
   }
 }
 

chrome/browser/ui/views/extensions/extension_installed_bubble_view.cc

@@ -90,6 +90,7 @@ views::View* AnchorViewForBrowser(ExtensionInstalledBubble* controller,
       BrowserActionsContainer* container =
           browser_view->toolbar()->browser_actions();
       // Hitting this DCHECK means |ShouldShow| failed.
+      DCHECK(container);
       DCHECK(!container->animating());
 
       reference_view = container->GetViewForId(controller->extension()->id());
@@ -405,7 +406,7 @@ bool ExtensionInstalledBubble::ShouldShow() {
         BrowserView::GetBrowserViewForBrowser(browser())
             ->toolbar()
             ->browser_actions();
-    return !container->animating();
+    return container && !container->animating();
   }
   return true;
 }

chrome/browser/ui/views/toolbar/media_router_action_platform_delegate_views.cc

@@ -39,7 +39,7 @@ bool MediaRouterActionPlatformDelegateViews::CloseOverflowMenuIfOpen() {
       BrowserView::GetBrowserViewForBrowser(browser_)
           ->toolbar()
           ->app_menu_button();
-  if (!app_menu_button->IsMenuShowing())
+  if (!app_menu_button || !app_menu_button->IsMenuShowing())
     return false;
 
   app_menu_button->CloseMenu();