Check that containers are supported by Chrome in requestMediaKeySystemAccess().

media/blink/webencryptedmediaclient_impl.cc

Index: media/blink/webencryptedmediaclient_impl.cc
diff --git a/media/blink/webencryptedmediaclient_impl.cc b/media/blink/webencryptedmediaclient_impl.cc
index ccd44fb528f562d24de1e35b02f771f25eacef0b..1c1f88ac2e6fd5e273c740151656895531d00deb 100644
--- a/media/blink/webencryptedmediaclient_impl.cc
+++ b/media/blink/webencryptedmediaclient_impl.cc
@@ -146,13 +146,16 @@ static bool IsSupportedContentType(
     return false;
   }
 
-  if (codec_vector.empty())
-    return true;
+  // Check that |container_mime_type| is supported by Chrome.
+  if (!net::IsSupportedMediaMimeType(container_lower))

[ddorwin, 2015/03/26 17:55:10]

This would allow, for example, "video/ogg", which is not supported encrypted.
Why doesn't IsSupportedCodecCombination() check the container when codec_vector
is empty?

[sandersd (OOO until July 31), 2015/03/26 18:11:05]

IsSupportedCodecCombination() already makes sure that the CDM supports the
container, so nothing exotic should show up here.

IsSupportedStrictMediaMimeType() returns Maybe when the container requires a
codec list and none is given (but also in other cases we don't support).

+    return false;
 
   // Check that |codecs| are supported by Chrome. This is done primarily to
   // validate extended codecs, but it also ensures that the CDM cannot support
   // codecs that Chrome does not (which could complicate the robustness
   // algorithm).
+  if (codec_vector.empty())
+    return true;
   codec_vector.clear();
   net::ParseCodecString(codecs, &codec_vector, false);
   return (net::IsSupportedStrictMediaMimeType(container_lower, codec_vector) ==