Add support for encrypted WebM files as defined in the RFC.

media/webm/webm_cluster_parser.cc

Index: media/webm/webm_cluster_parser.cc
diff --git a/media/webm/webm_cluster_parser.cc b/media/webm/webm_cluster_parser.cc
index 5b18c56e106a520df5e801b1a899a341a1ea8a7e..4e3ed33c6ebe9868c6077bb8585cc9694ad4b1cd 100644
--- a/media/webm/webm_cluster_parser.cc
+++ b/media/webm/webm_cluster_parser.cc
@@ -5,6 +5,7 @@
 #include "media/webm/webm_cluster_parser.h"
 
 #include "base/logging.h"
+#include "base/sys_byteorder.h"
 #include "media/base/data_buffer.h"
 #include "media/base/decrypt_config.h"
 #include "media/webm/webm_constants.h"
@@ -187,14 +188,26 @@ bool WebMClusterParser::OnBlock(int track_num, int timecode,
   base::TimeDelta timestamp = base::TimeDelta::FromMicroseconds(
       (cluster_timecode_ + timecode) * timecode_multiplier_);
 
+  bool encrypted = track_num == video_.track_num() &&
+                         video_encryption_key_id_.get();
+
   // The first bit of the flags is set when the block contains only keyframes.
   // http://www.matroska.org/technical/specs/index.html
   bool is_keyframe = (flags & 0x80) != 0;
   scoped_refptr<StreamParserBuffer> buffer =
       StreamParserBuffer::CopyFrom(data, size, is_keyframe);
 
-  if (track_num == video_.track_num() && video_encryption_key_id_.get()) {
+  if (encrypted) {
+    // Every encrypted Block has an HMAC and IV prepended to it. Current WebM
+    // encrypted request for comments specification is here
+    // http://wiki.webmproject.org/encryption/webm-encryption-rfc.
+    uint64 network_iv;
+    memcpy(&network_iv,
+           data + DecryptConfig::kWebMIntegrityCheckSize,
+           sizeof(network_iv));
+    const uint64 iv = base::NetToHost64(network_iv);
     buffer->SetDecryptConfig(scoped_ptr<DecryptConfig>(new DecryptConfig(
+        data, DecryptConfig::kWebMIntegrityCheckSize, iv,
         video_encryption_key_id_.get(), video_encryption_key_id_size_)));
   }