Create only a single LegacyRenderWidgetHostHWND per WebContentsViewAura.

content/browser/renderer_host/render_widget_host_view_aura.h

Index: content/browser/renderer_host/render_widget_host_view_aura.h
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.h b/content/browser/renderer_host/render_widget_host_view_aura.h
index 51942cd96d961b17e3b8be7071351206533562de..701c4d862f4e535f9ede0a2e38a2e8b237f424ed 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.h
+++ b/content/browser/renderer_host/render_widget_host_view_aura.h
@@ -204,6 +204,10 @@ class CONTENT_EXPORT RenderWidgetHostViewAura
                                        cc::SurfaceId original_surface,
                                        gfx::Point* transformed_point) override;
 
+#if defined(OS_WIN)
+  void SetLegacyRenderWidgetHostHWND(LegacyRenderWidgetHostHWND* legacy_hwnd);
+#endif
+
   // Overridden from ui::TextInputClient:
   void SetCompositionText(const ui::CompositionText& composition) override;
   void ConfirmCompositionText() override;
@@ -286,9 +290,6 @@ class CONTENT_EXPORT RenderWidgetHostViewAura
 
   // Updates the cursor clip region. Used for mouse locking.
   void UpdateMouseLockRegion();
-
-  // Notification that the LegacyRenderWidgetHostHWND was destroyed.
-  void OnLegacyWindowDestroyed();
 #endif
 
   // Method to indicate if this instance is shutting down or closing.
@@ -623,18 +624,8 @@ class CONTENT_EXPORT RenderWidgetHostViewAura
   // for accessibility, as the container for windowless plugins like
   // Flash/Silverlight, etc and for legacy drivers for trackpoints/trackpads,
   // etc.
-  // The LegacyRenderWidgetHostHWND instance is created during the first call
-  // to RenderWidgetHostViewAura::InternalSetBounds. The instance is destroyed
-  // when the LegacyRenderWidgetHostHWND hwnd is destroyed.
   content::LegacyRenderWidgetHostHWND* legacy_render_widget_host_HWND_;
 
-  // Set to true if the legacy_render_widget_host_HWND_ instance was destroyed
-  // by Windows. This could happen if the browser window was destroyed by
-  // DestroyWindow for e.g. This flag helps ensure that we don't try to create
-  // the LegacyRenderWidgetHostHWND instance again as that would be a futile
-  // exercise.
-  bool legacy_window_destroyed_;
-
   // Contains a copy of the last context menu request parameters. Only set when
   // we receive a request to show the context menu on a long press.
   std::unique_ptr<ContextMenuParams> last_context_menu_params_;