Mozart: Implement hit testing.

services/gfx/compositor/compositor_engine.cc

 // Copyright 2015 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 "services/gfx/compositor/compositor_engine.h"
 
 #include <algorithm>
 #include <sstream>
 #include <utility>
 
@@ skipping 258 matching lines @@
 }
 
 void CompositorEngine::HitTest(
     RendererState* renderer_state,
     mojo::PointPtr point,
     const mojo::gfx::composition::HitTester::HitTestCallback& callback) {
   DCHECK(IsRendererStateRegisteredDebug(renderer_state));
   DCHECK(point);
   DVLOG(1) << "HitTest: renderer=" << renderer_state << ", point=" << point;
 
-  // TODO(jeffbrown): hit tests on scenes
   auto result = mojo::gfx::composition::HitTestResult::New();
+
+  if (renderer_state->visible_snapshot()) {
+    DCHECK(!renderer_state->visible_snapshot()->is_blocked());
+    renderer_state->visible_snapshot()->HitTest(*point, result.get());
+  }
+
   callback.Run(result.Pass());
 }
 
 base::WeakPtr<SceneDef> CompositorEngine::ResolveSceneReference(
     const mojo::gfx::composition::SceneToken& scene_token) {
   SceneState* scene_state = FindScene(scene_token.value);
   return scene_state ? scene_state->scene_def()->GetWeakPtr()
                      : base::WeakPtr<SceneDef>();
 }
 
@@ skipping 168 matching lines @@
 
   SceneDef::Disposition disposition =
       PresentScene(scene_state, presentation_time);
   if (disposition == SceneDef::Disposition::kFailed)
     DestroyScene(scene_state);
   else if (disposition == SceneDef::Disposition::kSucceeded)
     InvalidateScene(scene_state);
 }
 
 }  // namespace compositor