Have uses of MockImageResourceClient leak less.

Source/core/fetch/MockImageResourceClient.h

 /*
  * Copyright (c) 2013, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 15 matching lines @@
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef MockImageResourceClient_h
 #define MockImageResourceClient_h
 
 #include "core/fetch/ImageResourceClient.h"
 
-#include <gtest/gtest.h>
+namespace blink {
 
-namespace blink {
+template<typename T> class ResourcePtr;
+
+class Resource;
 
 class MockImageResourceClient final : public ImageResourceClient {
 public:
-    MockImageResourceClient()
-        : m_imageChangedCount(0)
-        , m_notifyFinishedCalled(false)
-    {
-    }
+    explicit MockImageResourceClient(const ResourcePtr<Resource>&);
+    ~MockImageResourceClient() override;
 
-    ~MockImageResourceClient() override {}
     void imageChanged(ImageResource*, const IntRect*) override
     {
         m_imageChangedCount++;
     }
 
-    void notifyFinished(Resource*) override
-    {
-        ASSERT_FALSE(m_notifyFinishedCalled);
-        m_notifyFinishedCalled = true;
-    }
+    void notifyFinished(Resource*) override;
 
     int imageChangedCount() const { return m_imageChangedCount; }
     bool notifyFinishedCalled() const { return m_notifyFinishedCalled; }
 
+    void removeAsClient();
+
 private:
+    Resource* m_resource;
     int m_imageChangedCount;
     bool m_notifyFinishedCalled;
 };
 
 } // namespace blink
 
-#endif // ImageResourceTest_h
+#endif // MockImageResourceClient_h