Made double-tap zoom work in pinch virtual viewport mode (Chromium-side).

cc/test/layer_tree_test.h

Index: cc/test/layer_tree_test.h
diff --git a/cc/test/layer_tree_test.h b/cc/test/layer_tree_test.h
index 0f7aec35b9299ff181f82916e449a23c5ec22563..8860778825b482a42f0dc1e111981db8db5bfb9b 100644
--- a/cc/test/layer_tree_test.h
+++ b/cc/test/layer_tree_test.h
@@ -58,6 +58,10 @@ class TestHooks : public AnimationDelegate {
                                     bool has_unfinished_animation) {}
   virtual void WillAnimateLayers(LayerTreeHostImpl* host_impl,
                                  base::TimeTicks monotonic_time) {}
+  virtual void ApplyViewportDeltas(const gfx::Vector2d& inner_delta,
+                                   const gfx::Vector2d& outer_delta,
+                                   float scale,
+                                   float top_controls_delta) {}
   virtual void ApplyViewportDeltas(const gfx::Vector2d& scroll_delta,
                                    float scale,
                                    float top_controls_delta) {}