Bug 1038855, part 2 - Use an nsRefPtr for CompositorChild::SharedFrameMetricsData::mBuffer. r=bjacob

gfx/layers/ipc/CompositorChild.cpp

@@ -212,7 +212,6 @@ CompositorChild::SharedFrameMetricsData::SharedFrameMetricsData(
     const ipc::SharedMemoryBasic::Handle& metrics,
     const CrossProcessMutexHandle& handle,
     const uint32_t& aAPZCId) :
-    mBuffer(nullptr),
     mMutex(nullptr),
     mAPZCId(aAPZCId)
 {
@@ -227,7 +226,7 @@ CompositorChild::SharedFrameMetricsData::~SharedFrameMetricsData()
   // When the hash table deletes the class, delete
   // the shared memory and mutex.
   delete mMutex;
-  delete mBuffer;
+  mBuffer = nullptr;
   MOZ_COUNT_DTOR(SharedFrameMetricsData);
 }
 

gfx/layers/ipc/CompositorChild.h

@@ -100,7 +100,7 @@ private:
   private:
     // Pointer to the class that allows access to the shared memory that contains
     // the shared FrameMetrics
-    mozilla::ipc::SharedMemoryBasic* mBuffer;
+    nsRefPtr<mozilla::ipc::SharedMemoryBasic> mBuffer;
     CrossProcessMutex* mMutex;
     // Unique ID of the APZC that is sharing the FrameMetrics
     uint32_t mAPZCId;