Implement "Key Presence" step in "Encrypted Block Encounted" algorithm in EME.

media/filters/chunk_demuxer_unittest.cc

Index: media/filters/chunk_demuxer_unittest.cc
diff --git a/media/filters/chunk_demuxer_unittest.cc b/media/filters/chunk_demuxer_unittest.cc
index 927636acfc3827081cf6fceb2b607bcf775ffed8..ceb1bb9ac28b80ac791dd60b81931a4475f2d858 100644
--- a/media/filters/chunk_demuxer_unittest.cc
+++ b/media/filters/chunk_demuxer_unittest.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "base/bind.h"
+#include "base/message_loop.h"
 #include "media/base/audio_decoder_config.h"
 #include "media/base/decoder_buffer.h"
 #include "media/base/mock_callback.h"
@@ -669,6 +670,7 @@ class ChunkDemuxerTest : public testing::Test {
     return true;
   }
 
+  MessageLoop message_loop_;

[xhwang, 2012/07/30 20:48:25]

In the original test, since we don't have a message loop, MessageLoop::Current()
returns NULL. The test still works because it compares pointers directly (i.e.
if (NULL != NULL) ...):
http://code.google.com/searchframe#OAMlx_jo-ck/src/media/filters/chunk_demuxe...

But now we switch to MessageLoopProxy, this is caught by an assertion:
T* scoped_refptr<T>::operator->() const [with T = base::MessageLoopProxy]:
Assertion `ptr_ != __null' failed.

It makes sense for me to create a MessageLoop here so that we don't rely on the
"if (NULL != NULL)" logic. With this, all tests pass now.

   MockDemuxerHost host_;
 
   scoped_ptr<MockChunkDemuxerClient> client_;