EME: Correctly handle container-only contentType strings

media/blink/key_system_config_selector.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/blink/key_system_config_selector.h"
 
 #include <stddef.h>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 292 matching lines @@
 }
 
 // TODO(sandersd): Move contentType parsing from Blink to here so that invalid
 // parameters can be rejected. http://crbug.com/417561
 bool KeySystemConfigSelector::IsSupportedContentType(
     const std::string& key_system,
     EmeMediaType media_type,
     const std::string& container_mime_type,
     const std::string& codecs,
     KeySystemConfigSelector::ConfigState* config_state) {
+  // 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

[ddorwin, 2016/04/25 22:58:51]

If we want to exclude contentTypes without codecs once one capability has been
selected, we may need to move this to the call site where we have more context.

[jrummell, 2016/04/26 21:23:56]

Acknowledged.

+    // 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_mime_type != "audio/webm" &&

[ddorwin, 2016/04/25 22:58:51]

This assumes the string is lower case, but that doesn't happen until line 342
below.

Per step 3.6, comparison is case-insensitive. Thus, we should move that up to
the top of this function, since this function covers steps 3.4-.11 per the
comment at the call site. I think the TODO below is incorrect and can be
removed.

[jrummell, 2016/04/26 21:23:56]

Done.

+        container_mime_type != "video/webm" &&
+        container_mime_type != "audio/mp4" &&
+        container_mime_type != "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,
                               CanUseAesDecryptor(key_system))) {
     return false;
   }
 
   // TODO(servolk): Converting |container_mime_type| to lower-case could be
@@ skipping 480 matching lines @@
 
 void KeySystemConfigSelector::OnPermissionResult(
     scoped_ptr<SelectionRequest> request,
     bool is_permission_granted) {
   request->was_permission_requested = true;
   request->is_permission_granted = is_permission_granted;
   SelectConfigInternal(std::move(request));
 }
 
 }  // namespace media