Create only a single LegacyRenderWidgetHostHWND per WebContentsViewAura.

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index c33e325cef30eaab1a331b7c0dcf7f6d7f8f6166..207788f04e72b91678915c507d5a43bcc8be6104 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -382,7 +382,6 @@ RenderWidgetHostViewAura::RenderWidgetHostViewAura(RenderWidgetHost* host,
       cursor_visibility_state_in_renderer_(UNKNOWN),
 #if defined(OS_WIN)
       legacy_render_widget_host_HWND_(nullptr),
-      legacy_window_destroyed_(false),
 #endif
       has_snapped_to_boundary_(false),
       is_guest_view_hack_(is_guest_view_hack),
@@ -555,20 +554,6 @@ void RenderWidgetHostViewAura::Show() {
   }
 
   delegated_frame_host_->WasShown(browser_latency_info);
-
-#if defined(OS_WIN)
-  if (legacy_render_widget_host_HWND_) {
-    // Reparent the legacy Chrome_RenderWidgetHostHWND window to the parent
-    // window before reparenting any plugins. This ensures that the plugin
-    // windows stay on top of the child Zorder in the parent and receive
-    // mouse events, etc.
-    legacy_render_widget_host_HWND_->UpdateParent(
-        GetNativeView()->GetHost()->GetAcceleratedWidget());
-    legacy_render_widget_host_HWND_->SetBounds(
-        window_->GetBoundsInRootWindow());
-    legacy_render_widget_host_HWND_->Show();
-  }
-#endif
 }
 
 void RenderWidgetHostViewAura::Hide() {
@@ -578,16 +563,6 @@ void RenderWidgetHostViewAura::Hide() {
   if (host_ && !host_->is_hidden()) {
     host_->WasHidden();
     delegated_frame_host_->WasHidden();
-
-#if defined(OS_WIN)
-    aura::WindowTreeHost* host = window_->GetHost();
-    if (host) {
-      // We reparent the legacy Chrome_RenderWidgetHostHWND window to the global
-      // hidden window on the same lines as Windowed plugin windows.
-      if (legacy_render_widget_host_HWND_)
-        legacy_render_widget_host_HWND_->UpdateParent(ui::GetHiddenWindow());
-    }
-#endif
   }
 
 #if defined(OS_WIN)
@@ -1049,12 +1024,7 @@ void RenderWidgetHostViewAura::UpdateMouseLockRegion() {
           .ToRECT();
   ::ClipCursor(&window_rect);
 }
-
-void RenderWidgetHostViewAura::OnLegacyWindowDestroyed() {
-  legacy_render_widget_host_HWND_ = NULL;
-  legacy_window_destroyed_ = true;
-}
-#endif
+#endif  // defined(OS_WIN)
 
 void RenderWidgetHostViewAura::OnSwapCompositorFrame(
     uint32_t output_surface_id,
@@ -1089,6 +1059,13 @@ void RenderWidgetHostViewAura::DidStopFlinging() {
   selection_controller_client_->OnScrollCompleted();
 }
 
+#if defined(OS_WIN)
+void RenderWidgetHostViewAura::SetLegacyRenderWidgetHostHWND(
+    LegacyRenderWidgetHostHWND* legacy_hwnd) {
+  legacy_render_widget_host_HWND_ = legacy_hwnd;
+}
+#endif
+
 bool RenderWidgetHostViewAura::HasAcceleratedSurface(
     const gfx::Size& desired_size) {
   // Aura doesn't use GetBackingStore for accelerated pages, so it doesn't
@@ -1270,8 +1247,11 @@ RenderWidgetHostViewAura::CreateBrowserAccessibilityManager(
 gfx::AcceleratedWidget
 RenderWidgetHostViewAura::AccessibilityGetAcceleratedWidget() {
 #if defined(OS_WIN)
-  if (legacy_render_widget_host_HWND_)
-    return legacy_render_widget_host_HWND_->hwnd();
+  if (legacy_render_widget_host_HWND_) {
+    HWND hwnd = legacy_render_widget_host_HWND_->hwnd();
+    if (::IsWindow(hwnd))
+      return hwnd;
+  }
 #endif
   return gfx::kNullAcceleratedWidget;
 }
@@ -1687,19 +1667,15 @@ void RenderWidgetHostViewAura::OnDeviceScaleFactorChanged(
 
 void RenderWidgetHostViewAura::OnWindowDestroying(aura::Window* window) {
 #if defined(OS_WIN)
-  // The LegacyRenderWidgetHostHWND instance is destroyed when its window is
-  // destroyed. Normally we control when that happens via the Destroy call
-  // in the dtor. However there may be cases where the window is destroyed
-  // by Windows, i.e. the parent window is destroyed before the
-  // RenderWidgetHostViewAura instance goes away etc. To avoid that we
-  // destroy the LegacyRenderWidgetHostHWND instance here.
-  if (legacy_render_widget_host_HWND_) {
-    legacy_render_widget_host_HWND_->set_host(NULL);
-    legacy_render_widget_host_HWND_->Destroy();
-    // The Destroy call above will delete the LegacyRenderWidgetHostHWND
-    // instance.
-    legacy_render_widget_host_HWND_ = NULL;
+  HWND parent = NULL;
+  // If the tab was hidden and it's closed, host_->is_hidden would have been
+  // reset to false in RenderWidgetHostImpl::RendererExited.
+  if (!window_->GetRootWindow() || host_->is_hidden()) {
+    parent = ui::GetHiddenWindow();
+  } else {
+    parent = window_->GetHost()->GetAcceleratedWidget();
   }
+  legacy_render_widget_host_HWND_ = nullptr;
 #endif
 
   // Make sure that the input method no longer references to this object before
@@ -2280,13 +2256,6 @@ RenderWidgetHostViewAura::~RenderWidgetHostViewAura() {
     popup_child_host_view_->popup_parent_host_view_ = NULL;
   }
   event_filter_for_popup_exit_.reset();
-
-#if defined(OS_WIN)
-  // The LegacyRenderWidgetHostHWND window should have been destroyed in
-  // RenderWidgetHostViewAura::OnWindowDestroying and the pointer should
-  // be set to NULL.
-  DCHECK(!legacy_render_widget_host_HWND_);
-#endif
 }
 
 void RenderWidgetHostViewAura::CreateAuraWindow() {
@@ -2497,28 +2466,8 @@ void RenderWidgetHostViewAura::InternalSetBounds(const gfx::Rect& rect) {
     window_->SetBounds(rect);
   host_->WasResized();
   delegated_frame_host_->WasResized();
-#if defined(OS_WIN)
-  // Create the legacy dummy window which corresponds to the bounds of the
-  // webcontents. It is needed for accessibility and for scrolling to work in
-  // legacy drivers for trackpoints/trackpads, etc.
-  if (!legacy_window_destroyed_ && GetHostWindowHWND()) {
-    if (!legacy_render_widget_host_HWND_) {
-      legacy_render_widget_host_HWND_ =
-          LegacyRenderWidgetHostHWND::Create(GetHostWindowHWND());
-    }
-    if (legacy_render_widget_host_HWND_) {
-      legacy_render_widget_host_HWND_->set_host(this);
-      legacy_render_widget_host_HWND_->SetBounds(
-          window_->GetBoundsInRootWindow());
-      // There are cases where the parent window is created, made visible and
-      // the associated RenderWidget is also visible before the
-      // LegacyRenderWidgetHostHWND instace is created. Ensure that it is shown
-      // here.
-      if (!host_->is_hidden())
-        legacy_render_widget_host_HWND_->Show();
-    }
-  }
 
+#if defined(OS_WIN)
   if (mouse_locked_)
     UpdateMouseLockRegion();
 #endif
@@ -2564,13 +2513,6 @@ void RenderWidgetHostViewAura::AddedToRootWindow() {
       input_method->SetFocusedTextInputClient(this);
   }
 
-#if defined(OS_WIN)
-  // The parent may have changed here. Ensure that the legacy window is
-  // reparented accordingly.
-  if (legacy_render_widget_host_HWND_)
-    legacy_render_widget_host_HWND_->UpdateParent(GetHostWindowHWND());
-#endif
-
   delegated_frame_host_->SetCompositor(window_->GetHost()->compositor());
 }
 
@@ -2584,13 +2526,6 @@ void RenderWidgetHostViewAura::RemovingFromRootWindow() {
 
   window_->GetHost()->RemoveObserver(this);
   delegated_frame_host_->ResetCompositor();
-
-#if defined(OS_WIN)
-  // Update the legacy window's parent temporarily to the desktop window. It
-  // will eventually get reparented to the right root.
-  if (legacy_render_widget_host_HWND_)
-    legacy_render_widget_host_HWND_->UpdateParent(::GetDesktopWindow());
-#endif
 }
 
 void RenderWidgetHostViewAura::DetachFromInputMethod() {