Don't coerce pointers to compositor layer mappings to booleans.

Source/core/rendering/CompositedLayerMappingPtr.h

Index: Source/core/rendering/CompositedLayerMappingPtr.h
diff --git a/Source/core/rendering/CompositedLayerMappingPtr.h b/Source/core/rendering/CompositedLayerMappingPtr.h
new file mode 100644
index 0000000000000000000000000000000000000000..27cb68581d5ff74c2c7c4fda540350bbb71a19c6
--- /dev/null
+++ b/Source/core/rendering/CompositedLayerMappingPtr.h
@@ -0,0 +1,39 @@
+// 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.
+
+#ifndef CompositedLayerMappingPtr_h
+#define CompositedLayerMappingPtr_h
+
+#include "wtf/Assertions.h"
+
+namespace WebCore {
+
+class CompositedLayerMapping;
+
+class CompositedLayerMappingPtr {
+public:
+    CompositedLayerMappingPtr(CompositedLayerMapping* mapping)
+        : m_mapping(mapping)
+    {
+    }
+
+    CompositedLayerMapping& operator*() const
+    {
+        ASSERT(m_mapping);
+        return *m_mapping;
+    }
+
+    CompositedLayerMapping* operator->() const
+    {
+        ASSERT(m_mapping);
+        return m_mapping;
+    }
+
+private:
+    CompositedLayerMapping* m_mapping;
+};
+
+} // namespace WebCore
+
+#endif // CompositedLayerMappingPtr_h