Update from https://crrev.com/305340

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index ba4fabf09afdb746e9a9055b591a620be72afcf3..d1b29ca251dc6e7178f880fc7ad419d900d2e272 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -146,6 +146,10 @@ class CC_EXPORT LayerTreeHostImpl
   void PinchGestureUpdate(float magnify_delta,
                           const gfx::Point& anchor) override;
   void PinchGestureEnd() override;
+  void StartPageScaleAnimation(const gfx::Vector2d& target_offset,
+                               bool anchor_point,
+                               float page_scale,
+                               base::TimeDelta duration);
   void SetNeedsAnimate() override;
   bool IsCurrentlyScrollingLayerAt(const gfx::Point& viewport_point,
                                    InputHandler::ScrollInputType type) override;