Check for null return from GetNativeView().

chrome/browser/ui/ash/chrome_keyboard_ui.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/ash/chrome_keyboard_ui.h"
 
 #include <utility>
 
 #include "ash/common/shell_window_ids.h"
 #include "ash/root_window_controller.h"
@@ skipping 165 matching lines @@
 void ChromeKeyboardUI::ShowKeyboardContainer(aura::Window* container) {
   // TODO(bshe): Implement logic to decide which root window should display
   // virtual keyboard. http://crbug.com/303429
   if (container->GetRootWindow() != ash::Shell::GetPrimaryRootWindow())
     NOTIMPLEMENTED();
 
   KeyboardUIContent::ShowKeyboardContainer(container);
 }
 
 bool ChromeKeyboardUI::ShouldWindowOverscroll(aura::Window* window) const {
+  // Added while we determine if RenderWidgetHostViewChildFrame can be changed
+  // to always return a non-null value: https://crbug.com/644726 .
+  // If we cannot always return a non-null value, then this may need to stay.
+  if (!window)
+    return true;

[Charlie Reis, 2016/09/07 17:23:58]

I would suggest putting the null check in KeyboardUIContent::InitInsets instead.
 There's another caller of ShouldWindowOverscroll which passes
GetContainerWindow instead of GetNativeView, and we wouldn't want to paper over
a bug there if there was one.

[wjmaclean, 2016/09/07 17:41:05]

Done.

I also added a check in UpdateInsetsForWindow(), which is also a caller of
ShouldWindowOverscroll(), even though it seems less likely to be directly called
with a window* obtained from GetNativeView().

+
   aura::Window* root_window = window->GetRootWindow();
   if (!root_window)
     return true;
 
   if (root_window != GetKeyboardRootWindow())
     return false;
 
   ash::RootWindowController* root_window_controller =
       ash::GetRootWindowController(root_window);
   // Shell ime window container contains virtual keyboard windows and IME
@@ skipping 24 matching lines @@
   event_args->Append(input_context.release());
 
   std::unique_ptr<extensions::Event> event(new extensions::Event(
       extensions::events::VIRTUAL_KEYBOARD_PRIVATE_ON_TEXT_INPUT_BOX_FOCUSED,
       virtual_keyboard_private::OnTextInputBoxFocused::kEventName,
       std::move(event_args)));
   event->restrict_to_browser_context = browser_context();
   router->DispatchEventToExtension(kVirtualKeyboardExtensionID,
                                    std::move(event));
 }