Avoid sending empty OnRepaint msgs and propagate window damage correctly

content/renderer/render_widget.cc

 // Copyright (c) 2012 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 "content/renderer/render_widget.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
@@ skipping 1853 matching lines @@
 
   const SkBitmap& bitmap = skia::GetTopDevice(*canvas)->accessBitmap(false);
   if (!bitmap.copyTo(snapshot, SkBitmap::kARGB_8888_Config))
     return false;
 
   UMA_HISTOGRAM_TIMES("Renderer4.Snapshot",
                       base::TimeTicks::Now() - beginning_time);
   return true;
 }
 
-void RenderWidget::OnRepaint(const gfx::Size& size_to_paint) {
+void RenderWidget::OnRepaint(gfx::Size size_to_paint) {
   // During shutdown we can just ignore this message.
   if (!webwidget_)
     return;
 
+  // Even if the browser provides an empty damage rect, it's still expecting to
+  // receive a repaint ack so just damage the entire widget bounds.
+  if (size_to_paint.IsEmpty()) {
+    size_to_paint = size_;
+  }
+
   set_next_paint_is_repaint_ack();
-  if (is_accelerated_compositing_active_) {
-    if (compositor_)
-      compositor_->setNeedsRedraw();
-    scheduleComposite();
+  if (is_accelerated_compositing_active_ && compositor_) {
+    compositor_->SetNeedsRedrawRect(gfx::Rect(size_to_paint));
   } else {
     gfx::Rect repaint_rect(size_to_paint.width(), size_to_paint.height());
     didInvalidateRect(repaint_rect);
   }
 }
 
 void RenderWidget::OnSmoothScrollCompleted(int gesture_id) {
   PendingSmoothScrollGestureMap::iterator it =
       pending_smooth_scroll_gestures_.find(gesture_id);
   DCHECK(it != pending_smooth_scroll_gestures_.end());
@@ skipping 417 matching lines @@
 
   if (!context->Initialize(
           attributes,
           false /* bind generates resources */,
           CAUSE_FOR_GPU_LAUNCH_WEBGRAPHICSCONTEXT3DCOMMANDBUFFERIMPL_INITIALIZE))
     return NULL;
   return context.release();
 }
 
 }  // namespace content