Implement a method to access the non-composited content root layer picture pile.

cc/picture_pile_impl.cc

Index: cc/picture_pile_impl.cc
diff --git a/cc/picture_pile_impl.cc b/cc/picture_pile_impl.cc
index 05f9584ae58bb1f82306f7d244053b42a32909d1..f207256a302b916c36b92ff45bf754ca7389fc6c 100644
--- a/cc/picture_pile_impl.cc
+++ b/cc/picture_pile_impl.cc
@@ -89,4 +89,13 @@ void PicturePileImpl::GatherPixelRefs(
   }
 }
 
+gfx::Rect PicturePileImpl::LayerRect() const {
+  gfx::Rect layer_rect;
+  for (PicturePile::Pile::const_iterator i = pile_.begin();
+      i != pile_.end(); ++i) {
+    layer_rect.Union((*i)->LayerRect());
+  }
+  return layer_rect;
+}
+
 }  // namespace cc