Implement Chromium side of MediaKeys.isTypeSupported().

components/cdm/renderer/widevine_key_systems.cc

Index: components/cdm/renderer/widevine_key_systems.cc
diff --git a/components/cdm/renderer/widevine_key_systems.cc b/components/cdm/renderer/widevine_key_systems.cc
index 2a41322112eac5fac5e2dd64a7c46eff29705304..d08b6ad9239e6d242a1bd2cf3e9e3f9e545ae091 100644
--- a/components/cdm/renderer/widevine_key_systems.cc
+++ b/components/cdm/renderer/widevine_key_systems.cc
@@ -8,6 +8,7 @@
 #include <vector>
 
 #include "base/logging.h"
+#include "content/public/common/eme_constants.h"
 
 #include "widevine_cdm_version.h"  // In SHARED_INTERMEDIATE_DIR.
 
@@ -49,6 +50,16 @@ void AddWidevineWithCodecs(WidevineCdmType widevine_cdm_type,
   // initDataType.
   info.supported_codecs = supported_codecs;
 
+  // Here we assume that support for a container imples support for the
+  // associated initialization data type. KeySystems handles validating
+  // |init_data_type| x |container| pairings.
+  if (supported_codecs & content::EME_CODEC_WEBM_ALL)
+    info.supported_init_data_types |= content::EME_INIT_DATA_TYPE_WEBM;
+#if defined(USE_PROPRIETARY_CODECS)
+  if (supported_codecs & content::EME_CODEC_MP4_ALL)
+    info.supported_init_data_types |= content::EME_INIT_DATA_TYPE_CENC;
+#endif  // defined(USE_PROPRIETARY_CODECS)
+
 #if defined(ENABLE_PEPPER_CDMS)
   info.pepper_type = kWidevineCdmPluginMimeType;
 #endif  // defined(ENABLE_PEPPER_CDMS)