Implement Chromium side of MediaKeys.isTypeSupported().

components/cdm/renderer/android_key_systems.cc

Index: components/cdm/renderer/android_key_systems.cc
diff --git a/components/cdm/renderer/android_key_systems.cc b/components/cdm/renderer/android_key_systems.cc
index 99bc2bb5149db002453abca79267d494d2e57f7b..863a29bdfd81534e4bc942cf708c45f397c3c4bc 100644
--- a/components/cdm/renderer/android_key_systems.cc
+++ b/components/cdm/renderer/android_key_systems.cc
@@ -10,6 +10,8 @@
 #include "base/logging.h"
 #include "components/cdm/common/cdm_messages_android.h"
 #include "components/cdm/renderer/widevine_key_systems.h"
+#include "content/public/common/eme_codec.h"
+#include "content/public/common/eme_init_data_type.h"
 #include "content/public/renderer/render_thread.h"
 
 #include "widevine_cdm_version.h"  // In SHARED_INTERMEDIATE_DIR.
@@ -65,6 +67,9 @@ void AddAndroidPlatformKeySystems(
     if (response.compositing_codecs != content::EME_CODEC_NONE) {
       KeySystemInfo info(*it);
       info.supported_codecs = response.compositing_codecs;
+      // The MediaDrm API doesn't expose initDataTypes, but platform CDMs are
+      // not really trusted to implement them in a spec-compliant way anyway.

[ddorwin, 2014/09/13 01:20:44]

It's the key systems we're concerned about in this respect.

I think you could add CENC | WEBM, and let the supported containers (represented
by codecs???) determine which is actually exposed (by the logic that ensures
only logical combinations are reported as supported).

The current code would prevent anything beyond the key system name from being
checked.

[sandersd (OOO until July 31), 2014/09/22 23:45:52]

Done.

+      info.supported_init_data_types = content::EME_INIT_DATA_TYPE_NONE;
       concrete_key_systems->push_back(info);
     }
   }