Revert of Pass initDataType instead of contentType on OnNeedKey().

content/renderer/media/crypto/encrypted_media_player_support_impl.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 "content/renderer/media/crypto/encrypted_media_player_support_impl.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
@@ skipping 99 matching lines @@
   MediaKeyException result_id = MediaKeyExceptionForUMA(e);
   DCHECK_NE(result_id, kUnknownResultId) << e;
   EmeUMAHistogramEnumeration(
       key_system, method, result_id, kMaxMediaKeyException);
 }
 
 // Guess the type of |init_data|. This is only used to handle some corner cases
 // so we keep it as simple as possible without breaking major use cases.
 static std::string GuessInitDataType(const unsigned char* init_data,
                                      unsigned init_data_length) {
-  // Most WebM files use KeyId of 16 bytes. CENC init data is always >16 bytes.
+  // Most WebM files use KeyId of 16 bytes. MP4 init data are always >16 bytes.
   if (init_data_length == 16)
-    return "webm";
+    return "video/webm";
 
-  return "cenc";
+  return "video/mp4";
 }
 
 scoped_ptr<media::EncryptedMediaPlayerSupport>
 EncryptedMediaPlayerSupportImpl::Create(blink::WebMediaPlayerClient* client) {
   return scoped_ptr<EncryptedMediaPlayerSupport>(
       new EncryptedMediaPlayerSupportImpl(client));
 }
 
 EncryptedMediaPlayerSupportImpl::EncryptedMediaPlayerSupportImpl(
     blink::WebMediaPlayerClient* client)
@@ skipping 328 matching lines @@
 
   if (web_cdm_) {
     decryptor_ready_cb.Run(web_cdm_->GetDecryptor(), base::Bind(DoNothing));
     return;
   }
 
   decryptor_ready_cb_ = decryptor_ready_cb;
 }
 
 }  // namespace content