Fix large mis-paint when resizing windows aura chrome

ui/compositor/compositor.cc

Index: ui/compositor/compositor.cc
===================================================================
--- ui/compositor/compositor.cc	(revision 188861)
+++ ui/compositor/compositor.cc	(working copy)
@@ -410,6 +410,7 @@
       last_started_frame_(0),
       last_ended_frame_(0),
       disable_schedule_composite_(false),
+      is_resizing_ (false),
       compositor_lock_(NULL) {
   root_web_layer_ = cc::Layer::Create();
   root_web_layer_->SetAnchorPoint(gfx::PointF(0.f, 0.f));
@@ -496,6 +497,14 @@
   host_->set_has_transparent_background(host_has_transparent_background);
 }
 
+#if defined (OS_WIN)
+#ifndef NDEBUG
+const int kResizePaintLatency = 12 * 16;
+#else
+const int kResizePaintLatency = 4 * 16;
+#endif
+#endif  // OS_WIN.
+
 void Compositor::Draw(bool force_clear) {
   DCHECK(!g_compositor_thread);
 
@@ -509,6 +518,19 @@
     // compositeImmediately() directly.
     layout();
     host_->Composite(base::TimeTicks::Now());
+
+#if defined(OS_WIN)
+    // While we resize, we are usually a few frames behind. By blocking
+    // the UI thread here we minize the area that is mis-painted, specially
+    // in the non-client area. See RenderWidgetHostViewAura::SetBounds for
+    // more details.
+    if (is_resizing_ && (last_ended_frame_ > 1)) {

[cpu_(ooo_6.6-7.5), 2013/04/04 02:09:07]

when chrome starts we hit here with frames 0 and 1, so I check for that so that
I don't jank startup.

+      is_resizing_ = false;
+      base::PlatformThread::Sleep(
+          base::TimeDelta::FromMilliseconds(kResizePaintLatency));

[jonathan.backer, 2013/04/04 17:25:09]

My experience has been that there are a lot of events that bounce through the UI
thread. Blocking the UI thread for 50-200 ms is going to slow them down.

I'm familiar with the ResizeLock code. I'm going to get a win_aura build running
today (it's been months since I've built on windows --- I'll probably just pave
everything).

Once I understand the problem, hopefully I can be more constructive. A quick
glance at the code suggests we probably want to synchronize the
|root_web_layer_| SetBounds with the ResizeLock.

+    }
+#endif
+
   }
   if (!pending_swap.posted())
     NotifyEnd();
@@ -539,6 +561,8 @@
     size_ = size_in_pixel;
     host_->SetViewportSize(size_in_pixel, size_in_pixel);
     root_web_layer_->SetBounds(size_in_pixel);
+
+    is_resizing_ = true;
   }
   if (device_scale_factor_ != scale) {
     device_scale_factor_ = scale;