Implement Chromium side of MediaKeys.isTypeSupported().

content/renderer/media/crypto/key_systems.h

Index: content/renderer/media/crypto/key_systems.h
diff --git a/content/renderer/media/crypto/key_systems.h b/content/renderer/media/crypto/key_systems.h
index 99825d1997a7d8cf17129cbfcdbc51dcf4ceca4b..c9913282c727f68acc5097ff82ce1e6be8b174b1 100644
--- a/content/renderer/media/crypto/key_systems.h
+++ b/content/renderer/media/crypto/key_systems.h
@@ -24,6 +24,16 @@ std::string GetUnprefixedKeySystemName(const std::string& key_system);
 // Gets the prefixed key system name for |key_system|.
 std::string GetPrefixedKeySystemName(const std::string& key_system);
 
+bool IsSaneInitDataTypeWithContainer(

[ddorwin, 2014/09/23 22:48:17]

This is really an implementation detail of this class - we don't add every
combination in our table. Thus, this should probably be handled internally.
However, we don't have a function that checks the type and container, so I guess
we'll have to leave it exposed (unless/until the spec is updated to separate
them :) ).

[ddorwin, 2014/09/23 22:48:17]

This probably deserves a comment:
// Returns false if a container-specific |init_data_type| is specified with an
inappropriate container.

[sandersd (OOO until July 31), 2014/09/24 22:22:34]

Done.

[sandersd (OOO until July 31), 2014/09/24 22:22:34]

Acknowledged.

+    const std::string& init_data_type,

[ddorwin, 2014/09/23 22:48:17]

I was thinking we should convert IDT (and maybe container) to an enum to pass
around. (In a separate CL/effort.) WDYT?

[sandersd (OOO until July 31), 2014/09/24 22:22:34]

This makes sense; we could add APIs here to turn the string into enum values,
then use those values everywhere else.

For this particular method it doesn't make much difference.

[ddorwin, 2014/09/27 00:41:24]

Even better, the strings should never reach Chromium. :)

+    const std::string& container);
+
+bool IsSupportedKeySystem(const std::string& key_system);
+
+bool IsSupportedKeySystemWithInitDataType(
+    const std::string& key_system,
+    const std::string& init_data_type);
+
 // Returns whether |key_system| is a real supported key system that can be
 // instantiated.
 // Abstract parent |key_system| strings will return false.