V8ScriptValueSerializer: Add a separate version 'envelope' for Blink format version.

content/browser/android/string_message_codec.cc

 // Copyright 2017 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/browser/android/string_message_codec.h"
 
 #include <vector>
 
 #include "base/logging.h"
 
@@ skipping 96 matching lines @@
   memcpy(destination, &buffer[0], buffer.size());
   return result;
 }
 
 bool DecodeStringMessage(const base::string16& encoded_data,
                          base::string16* result) {
   size_t num_bytes = encoded_data.size() * 2;
 
   const uint8_t* ptr = reinterpret_cast<const uint8_t*>(&encoded_data[0]);
   const uint8_t* end = ptr + num_bytes;
+  uint8_t tag;
 
-  uint8_t tag;
-  if (!ReadUint8(&ptr, end, &tag) || tag != kVersionTag)
-    return false;
-
-  uint32_t version;
-  if (!ReadUint32(&ptr, end, &version))
-    return false;
-
+  // Discard any leading version and padding tags.
+  // There may be more than one version, due to Blink and V8 having separate
+  // version tags.
   do {
     if (!ReadUint8(&ptr, end, &tag))
       return false;
-  } while (tag == kPaddingTag);
+    uint32_t version;
+    if (tag == kVersionTag && !ReadUint32(&ptr, end, &version))
+      return false;
+  } while (tag == kVersionTag || tag == kPaddingTag);
 
   switch (tag) {
     case kOneByteStringTag: {
       uint32_t num_bytes;
       if (!ReadUint32(&ptr, end, &num_bytes))
         return false;
       result->assign(reinterpret_cast<const char*>(ptr),
                      reinterpret_cast<const char*>(ptr) + num_bytes);
       return true;
     }
     case kTwoByteStringTag: {
       uint32_t num_bytes;
       if (!ReadUint32(&ptr, end, &num_bytes))
         return false;
       result->assign(reinterpret_cast<const base::char16*>(ptr), num_bytes / 2);
       return true;
     }
   }
 
   DLOG(WARNING) << "Unexpected tag: " << tag;
   return false;
 }
 
 }  // namespace content