Clamps to invalidation region of a PictureLayer to the layer bounds to avoid adding unecessary bulk

cc/picture_layer.cc

Index: cc/picture_layer.cc
diff --git a/cc/picture_layer.cc b/cc/picture_layer.cc
index 4f192da7e180fdb51eaa7071aaad1d5107143fce..4e7bbff44b63d467e14ff2b93066c7e32c3e9e5b 100644
--- a/cc/picture_layer.cc
+++ b/cc/picture_layer.cc
@@ -51,7 +51,14 @@ void PictureLayer::setLayerTreeHost(LayerTreeHost* host) {
 
 void PictureLayer::setNeedsDisplayRect(const gfx::RectF& layer_rect) {
   gfx::Rect rect = gfx::ToEnclosedRect(layer_rect);
-  pending_invalidation_.Union(rect);
+  if (!rect.IsEmpty()) {

[danakj, 2013/01/09 00:31:57]

you could also rect.Intersect(gfx::Rect(contentBounds()) to do this on one line.

+    // Clamp invalidation to the layer bounds.
+    gfx::Rect clamped_rect = gfx::IntersectRects(
+        rect,
+        gfx::Rect(contentBounds()));
+    if (!clamped_rect.IsEmpty())
+      pending_invalidation_.Union(clamped_rect);

[danakj, 2013/01/09 00:31:57]

union with an empty rect is a no-op, so you probably don't need the if()?

+  }
   Layer::setNeedsDisplayRect(layer_rect);
 }