Aura: Compensate for round-off error in damage.

We get sub-DIP damage from the renderer with --ui-enable-partial-swap. When we convert to DIP in RWHVA::AccelerateSurfacePostSubBuffers, we trancate that damage (an shrink the rect). The straightforward solution is to assume that the damage was truncated and dilate the DIP damage rect.

BUG=139208
TEST=by hand on device that supports --ui-enable-partial-swap


Review URL: https://chromiumcodereview.appspot.com/10821054

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@148800 0039d316-1c4b-4281-b951-d872f2087c98

content/browser/renderer_host/render_widget_host_view_aura.cc

@@ -711,6 +711,12 @@ void RenderWidgetHostViewAura::AcceleratedSurfacePostSubBuffer(
             params_in_pixel.height,
         params_in_pixel.width,
         params_in_pixel.height));
+
+    // Damage may not have been DIP aligned, so inflate damage to compensate
+    // for any round-off error.
+    rect_to_paint.Inset(-1, -1);
+    rect_to_paint.Intersect(window_->bounds());
+
     window_->SchedulePaintInRect(rect_to_paint);
 
     if (!resize_locks_.empty()) {