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..98d668b9cb9989696c1a3b312b61b1e56ca9c240 100644
--- a/content/renderer/media/crypto/key_systems.h
+++ b/content/renderer/media/crypto/key_systems.h
@@ -24,6 +24,22 @@ 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);
 
+// Returns false if a container-specific |init_data_type| is specified with an
+// inappropriate container.
+// TODO(sandersd): Remove this essentailly internal detail if the spec is
+// updated to not convolve the two in a single method call.
+// TODO(sandersd): Use enum values instead of strings. http://crbug.com/417440
+bool IsSaneInitDataTypeWithContainer(
+    const std::string& init_data_type,
+    const std::string& container);
+
+// Note: Shouldn't be used for prefixed API as the old path reports UMAs.

[ddorwin, 2014/09/29 18:53:52]

"old path" isn't clear to future readers. I assume you mean
"IsSupportedKeySystemWithMediaMimeType()."

[sandersd (OOO until July 31), 2014/09/29 19:52:12]

Done.

+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.