cc: Expose clear and swap on Region

cc/layer_tree_host_unittest.cc

 // Copyright 2011 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 "config.h"
 
 #include "cc/layer_tree_host.h"
 
 #include "base/synchronization/lock.h"
 #include "cc/content_layer.h"
@@ skipping 1621 matching lines @@
     virtual void update(ResourceUpdateQueue&, const OcclusionTracker* occlusion, RenderingStats&) OVERRIDE
     {
         // Gain access to internals of the OcclusionTracker.
         const TestOcclusionTracker* testOcclusion = static_cast<const TestOcclusionTracker*>(occlusion);
         m_occludedScreenSpace = testOcclusion ? testOcclusion->occlusionInScreenSpace() : Region();
     }
 
     virtual bool drawsContent() const OVERRIDE { return true; }
 
     const Region& occludedScreenSpace() const { return m_occludedScreenSpace; }
-    void clearOccludedScreenSpace() { m_occludedScreenSpace = Region(); }
+    void clearOccludedScreenSpace() { m_occludedScreenSpace.Clear(); }
 
 private:
     TestLayer() : Layer() { }
     virtual ~TestLayer() { }
 
     Region m_occludedScreenSpace;
 };
 
 static void setTestLayerPropertiesForTesting(TestLayer* layer, Layer* parent, const WebTransformationMatrix& transform, const gfx::PointF& anchor, const gfx::PointF& position, const gfx::Size& bounds, bool opaque)
 {
@@ skipping 1572 matching lines @@
     int m_numCommitsDeferred;
     int m_numCompleteCommits;
 };
 
 TEST_F(LayerTreeHostTestDeferCommits, runMultiThread)
 {
     runTest(true);
 }
 
 }  // anonymous namespace