Fix native fault in WVMMediaSource::DecryptCallback

This change resolves a lifetime issue between the media extractor
and media sources.  The extractor was being passed as a context
object to a callout in the WV libs.  In some cases, a pointer to
the extractor would be delivered to the callout after the extractor
had been released.  This change assigns the responsibility of the
lifetime of the context object to the media source, to ensure that
a ref is always held on the context object during the lifetime of
the media source.

Change-Id: Ic7a57a1c8496a4798fe590ec356b8a19a4f69967
related-to-bug: 6502322

proprietary/wvm/include/WVMMediaSource.h

@@ -13,6 +13,7 @@
 #include <media/stagefright/MetaData.h>
 #include <media/stagefright/MediaBufferGroup.h>
 #include <utils/RefBase.h>
+#include "ClientContext.h"
 #ifdef REQUIRE_SECURE_BUFFERS
 #include "OEMCrypto_L1.h"
 #endif
@@ -29,6 +30,7 @@ public:
 
     void delegateFileSource(sp<WVMFileSource> fileSource);
     void delegateDataSource(sp<DataSource> dataSource);
+    void delegateClientContext(sp<ClientContext> context);
 
     virtual status_t start(MetaData *params = NULL);
     virtual status_t stop();
@@ -87,6 +89,7 @@ private:
 
     sp<WVMFileSource> mFileSource;
     sp<DataSource> mDataSource;
+    sp<ClientContext> mClientContext;
 
     Vector<size_t> mEncryptedSizes;