Fix VR Shell crashing when renderer crashes or native page is shown.

chrome/browser/android/vr_shell/vr_input_manager.cc

 // Copyright 2016 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/android/vr_shell/vr_input_manager.h"
 
 #include "base/task_runner_util.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/browser/render_widget_host_view.h"
@@ skipping 62 matching lines @@
   result.x = x / dpi_scale_;
   result.y = y / dpi_scale_;
   result.timeStampSeconds = time_ms / 1000.0;
   result.sourceDevice = blink::WebGestureDeviceTouchpad;
 
   return result;
 }
 
 void VrInputManager::ForwardGestureEvent(
     const blink::WebGestureEvent& gesture) {
+  if (!web_contents_->GetRenderWidgetHostView())
+    return;
   content::RenderWidgetHost* rwh =
       web_contents_->GetRenderWidgetHostView()->GetRenderWidgetHost();
   if (rwh)
     rwh->ForwardGestureEvent(gesture);
 }
 
 void VrInputManager::ForwardMouseEvent(
     const blink::WebMouseEvent& mouse_event) {
+  if (!web_contents_->GetRenderWidgetHostView())
+      return;
   content::RenderWidgetHost* rwh =
       web_contents_->GetRenderWidgetHostView()->GetRenderWidgetHost();
   if (rwh)
     rwh->ForwardMouseEvent(mouse_event);
 }
 
 }  // namespace vr_shell