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

mojo/examples/compositor_app/compositor_host.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "mojo/examples/compositor_app/compositor_host.h"
 
 #include "cc/layers/layer.h"
 #include "cc/layers/solid_color_layer.h"
 #include "cc/output/begin_frame_args.h"
 #include "cc/output/context_provider.h"
@@ skipping 54 matching lines @@
   double time_in_seconds = (args.frame_time - base::TimeTicks()).InSecondsF();
   double child_rotation_degrees = kDegreesPerSecond * time_in_seconds;
   gfx::Transform child_transform;
   child_transform.Translate(200, 200);
   child_transform.Rotate(child_rotation_degrees);
   child_layer_->SetTransform(child_transform);
   tree_->SetNeedsAnimate();
 }
 
 void CompositorHost::Layout() {}
+void CompositorHost::ApplyViewportDeltas(const gfx::Vector2d& inner_delta,
+                                         const gfx::Vector2d& outer_delta,
+                                         float page_scale,
+                                         float top_controls_delta) {}
 void CompositorHost::ApplyViewportDeltas(const gfx::Vector2d& scroll_delta,
                                          float page_scale,
                                          float top_controls_delta) {}
 
 scoped_ptr<cc::OutputSurface> CompositorHost::CreateOutputSurface(
     bool fallback) {
   return make_scoped_ptr(
       new cc::OutputSurface(
           new ContextProviderMojo(command_buffer_handle_.Pass())));
 }
 
 void CompositorHost::DidInitializeOutputSurface() {
 }
 
 void CompositorHost::WillCommit() {}
 void CompositorHost::DidCommit() {}
 void CompositorHost::DidCommitAndDrawFrame() {}
 void CompositorHost::DidCompleteSwapBuffers() {}
 
 }  // namespace examples
 }  // namespace mojo