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

media/webm/webm_content_encodings_client.cc

Index: media/webm/webm_content_encodings_client.cc
diff --git a/media/webm/webm_content_encodings_client.cc b/media/webm/webm_content_encodings_client.cc
index 086f85b60b5e8151488f5e97cc7d2bcafa7a50f7..a24b4bfa672946cdfbc8a475bbb709b104b391ef 100644
--- a/media/webm/webm_content_encodings_client.cc
+++ b/media/webm/webm_content_encodings_client.cc
@@ -50,6 +50,11 @@ WebMParserClient* WebMContentEncodingsClient::OnListStart(int id) {
     return this;
   }
 
+  if (id == kWebMIdContentEncAESSettings) {
+    DCHECK(cur_content_encoding_.get());
+    return this;
+  }
+
   // This should not happen if WebMListParser is working properly.
   DCHECK(false);
   return NULL;
@@ -121,6 +126,13 @@ bool WebMContentEncodingsClient::OnListEnd(int id) {
     return true;
   }
 
+  if (id == kWebMIdContentEncAESSettings) {
+    if (cur_content_encoding_->cipher_mode() ==
+        ContentEncoding::kCipherModeInvalid)
+      cur_content_encoding_->set_cipher_mode(ContentEncoding::kCipherModeCtr);
+    return true;
+  }
+
   // This should not happen if WebMListParser is working properly.
   DCHECK(false);
   return false;
@@ -206,6 +218,23 @@ bool WebMContentEncodingsClient::OnUInt(int id, int64 val) {
     return true;
   }
 
+  if (id == kWebMIdAESSettingsCipherMode) {
+    if (cur_content_encoding_->cipher_mode() !=
+        ContentEncoding::kCipherModeInvalid) {
+      DVLOG(1) << "Unexpected multiple AESSettingsCipherMode.";
+      return false;
+    }
+
+    if (val != ContentEncoding::kCipherModeCtr) {
+      DVLOG(1) << "Unexpected AESSettingsCipherMode " << val << ".";
+      return false;
+    }
+
+    cur_content_encoding_->set_cipher_mode(
+        static_cast<ContentEncoding::CipherMode>(val));
+    return true;
+  }
+
   // This should not happen if WebMListParser is working properly.
   DCHECK(false);
   return false;