Make a hole only as big as is necessary.

chrome/browser/renderer_host/render_widget_host_view_views.cc

Index: chrome/browser/renderer_host/render_widget_host_view_views.cc
diff --git a/chrome/browser/renderer_host/render_widget_host_view_views.cc b/chrome/browser/renderer_host/render_widget_host_view_views.cc
index c6be0b356c3060936e84e04db8411458451fd6e6..63399f5c389450b71ef6e0355d534b597934d801 100644
--- a/chrome/browser/renderer_host/render_widget_host_view_views.cc
+++ b/chrome/browser/renderer_host/render_widget_host_view_views.cc
@@ -355,12 +355,6 @@ void RenderWidgetHostViewViews::Paint(gfx::Canvas* canvas) {
     return;
   }
 
-  // Paint a "hole" in the canvas so that the render of the web page is on
-  // top of whatever else has already been painted in the views hierarchy.
-  // Later views might still get to paint on top.
-  canvas->FillRectInt(SK_ColorBLACK, 0, 0, kMaxWindowWidth, kMaxWindowHeight,
-                      SkXfermode::kClear_Mode);
-
   // Don't do any painting if the GPU process is rendering directly
   // into the View.
   RenderWidgetHost* render_widget_host = GetRenderWidgetHost();
@@ -385,6 +379,15 @@ void RenderWidgetHostViewViews::Paint(gfx::Canvas* canvas) {
 
   gfx::Rect paint_rect = gfx::Rect(0, 0, kMaxWindowWidth, kMaxWindowHeight);
   paint_rect = paint_rect.Intersect(invalid_rect_);
+  // Make sure we paint within the bounds.
+  paint_rect = paint_rect.Intersect(bounds());
+
+  // Paint a "hole" in the canvas so that the render of the web page is on
+  // top of whatever else has already been painted in the views hierarchy.
+  // Later views might still get to paint on top.
+  canvas->FillRectInt(SK_ColorBLACK, 0, 0,
+                      paint_rect.width(), paint_rect.height(),
+                      SkXfermode::kClear_Mode);

[Alex Nicolaou, 2011/01/21 16:00:16]

You'll have to move this back up.

If you're really worried about it, it would also be great to address the TODO on
line 370 which is 99% of the inefficiency here.

[sadrul, 2011/01/21 16:36:19]

Moved this back up.

 
   if (backing_store) {
     // Only render the widget if it is attached to a window; there's a short