EME: Correctly handle container-only contentType strings

media/blink/key_system_config_selector.cc

Index: media/blink/key_system_config_selector.cc
diff --git a/media/blink/key_system_config_selector.cc b/media/blink/key_system_config_selector.cc
index 885049c83872d0e5f80ec16863f6b8a501777af0..9e933f37a157ec9ce5fe7efbf69817251d600cda 100644
--- a/media/blink/key_system_config_selector.cc
+++ b/media/blink/key_system_config_selector.cc
@@ -310,20 +310,33 @@ bool KeySystemConfigSelector::IsSupportedContentType(
     const std::string& container_mime_type,
     const std::string& codecs,
     KeySystemConfigSelector::ConfigState* config_state) {
+  // From RFC6838: "Both top-level type and subtype names are case-insensitive."
+  std::string container_lower = base::ToLowerASCII(container_mime_type);
+
+  // contentTypes must provide a codec string unless the container implies a
+  // particular codec. For EME, none of the currently supported containers
+  // imply a codec, so |codecs| must be provided.
+  if (codecs.empty()) {
+    // Since the spec didn't initially require this, add an exemption for
+    // some existing containers to give clients time to adapt.
+    // TODO(jrummell): Remove this exemption once the number of contentTypes
+    // without codecs drops low enough (UMA added in the blink code).
+    // http://crbug.com/605661.
+    if (container_lower != "audio/webm" && container_lower != "video/webm" &&
+        container_lower != "audio/mp4" && container_lower != "video/mp4") {
+      return false;
+    }
+  }
+
   // Check that |container_mime_type| and |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 (!IsSupportedMediaFormat(container_mime_type, codecs,
+  if (!IsSupportedMediaFormat(container_lower, codecs,
                               CanUseAesDecryptor(key_system))) {
     return false;
   }
 
-  // TODO(servolk): Converting |container_mime_type| to lower-case could be
-  // moved to KeySystemsImpl::GetContentTypeConfigRule, plus we could add some
-  // upper-case container name test cases in media/base/key_systems_unittest.cc.
-  std::string container_lower = base::ToLowerASCII(container_mime_type);
-
   // Check that |container_mime_type| and |codecs| are supported by the CDM.
   // This check does not handle extended codecs, so extended codec information
   // is stripped (extended codec information was checked above).