Fixes bug in RootViewGtk where we we might not paint correctly if...

views/widget/root_view_gtk.cc

Index: views/widget/root_view_gtk.cc
===================================================================
--- views/widget/root_view_gtk.cc	(revision 19280)
+++ views/widget/root_view_gtk.cc	(working copy)
@@ -13,8 +13,19 @@
 namespace views {
 
 void RootView::OnPaint(GdkEventExpose* event) {
+  gfx::Rect original_dirty_region = GetScheduledPaintRectConstrainedToSize();
+  if (!original_dirty_region.IsEmpty()) {
+    // Between the the time the paint was scheduled and the time we end
+    // up painting more SchedulePaints may have been invoked. Expand the
+    // region Gdk wants us to paint to include the region we want to paint
+    // to make sure everything is painted. Otherwise we may not paint
+    // everything we need to.
+    gfx::Rect complete_area =
+        original_dirty_region.Union(gfx::Rect(event->area));
+    event->area = complete_area.ToGdkRectangle();
+  }
+
   gfx::CanvasPaint canvas(event);
-
   if (!canvas.is_empty()) {
     canvas.set_composite_alpha(
         static_cast<WidgetGtk*>(GetWidget())->is_transparent());