Fix large mis-paint when resizing windows aura chrome

See bug attached for screenshots

The CL does two things:
- Disables the resizer lock, so that UI bits can go ahead of content bits
- Janks (blocks) the UI thread until the compositor has flushed / finished
the pending commands.

This makes the mis-draw way less, up to one frame behind, which at my regular
mouse speed of 1.2 pixels / ms comes out to 20 pixels of whiteout.


BUG=177115
TEST=none
Review URL: https://codereview.chromium.org/13604007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@192657 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 9 insertions, 0 deletions

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 443eee9..adc258a 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -771,6 +771,14 @@ void RenderWidgetHostViewAura::SetBounds(const gfx::Rect& rect) {
       if (!compositor->HasObserver(this))
         compositor->AddObserver(this);
 
+// On Windows while resizing, the the resize locks makes us mis-paint a white
+// vertical strip (including the non-client area) if the content composition is
+// lagging the UI composition. So here we disable the throttling so that the UI
+// bits can draw ahead of the content thereby reducing the amount of whiteout.
+// Because this causes the content to be drawn at wrong sizes while resizing
+// we compensate by blocking the UI thread in Compositor::Draw() by issuing a
+// FinishAllRendering() if we are resizing.
+#if !defined (OS_WIN)
       bool defer_compositor_lock =
          can_lock_compositor_ == NO_PENDING_RENDERER_FRAME ||
          can_lock_compositor_ == NO_PENDING_COMMIT;
@@ -780,6 +788,7 @@ void RenderWidgetHostViewAura::SetBounds(const gfx::Rect& rect) {
 
       resize_locks_.push_back(make_linked_ptr(
           new ResizeLock(root_window, rect.size(), defer_compositor_lock)));
+#endif
     }
   }
   window_->SetBounds(rect);