Only draw the overhang pattern on overhang areas.

cc/trees/layer_tree_impl.cc

Index: cc/trees/layer_tree_impl.cc
diff --git a/cc/trees/layer_tree_impl.cc b/cc/trees/layer_tree_impl.cc
index 4604043663920750438b5de260b0d8a0249d36b2..ad4060f04c8158b2fbd90abd783fb0682017e27b 100644
--- a/cc/trees/layer_tree_impl.cc
+++ b/cc/trees/layer_tree_impl.cc
@@ -7,6 +7,8 @@
 #include "base/debug/trace_event.h"
 #include "cc/animation/keyframed_animation_curve.h"
 #include "cc/animation/scrollbar_animation_controller.h"
+#include "cc/base/math_util.h"
+#include "cc/base/util.h"
 #include "cc/debug/traced_value.h"
 #include "cc/layers/heads_up_display_layer_impl.h"
 #include "cc/layers/layer.h"
@@ -238,6 +240,15 @@ gfx::SizeF LayerTreeImpl::ScrollableViewportSize() const {
                         1.0f / total_page_scale_factor());
 }
 
+gfx::Rect LayerTreeImpl::RootScrollLayerDeviceViewportBounds() const {
+  if (!root_scroll_layer_ || root_scroll_layer_->children().empty())
+    return gfx::Rect();
+  LayerImpl* layer = root_scroll_layer_->children()[0];
+  return MathUtil::MapClippedRect(
+      layer->screen_space_transform(),
+      gfx::Rect(layer->content_bounds()));
+}
+
 void LayerTreeImpl::UpdateMaxScrollOffset() {
   LayerImpl* root_scroll = RootScrollLayer();
   if (!root_scroll || !root_scroll->children().size())