Chromecast: use weak pointers for AvPipelineImpl callbacks on CMA thread.

chromecast/media/cma/pipeline/av_pipeline_impl.h

Index: chromecast/media/cma/pipeline/av_pipeline_impl.h
diff --git a/chromecast/media/cma/pipeline/av_pipeline_impl.h b/chromecast/media/cma/pipeline/av_pipeline_impl.h
index 7c917ae521030e40c7771142a336b2d7e3815555..591c87fed5502e4b260b345c6b0d6bb0b5b92132 100644
--- a/chromecast/media/cma/pipeline/av_pipeline_impl.h
+++ b/chromecast/media/cma/pipeline/av_pipeline_impl.h
@@ -10,6 +10,7 @@
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/thread_checker.h"
 #include "chromecast/media/cma/backend/media_component_device.h"
@@ -167,6 +168,9 @@ class AvPipelineImpl : public base::RefCountedThreadSafe<AvPipelineImpl> {
   BrowserCdmCast* media_keys_;
   int media_keys_callback_id_;
 
+  base::WeakPtr<AvPipelineImpl> weak_this_;
+  base::WeakPtrFactory<AvPipelineImpl> weak_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(AvPipelineImpl);
 };