Refactor Pickle Read methods to use higher performance PickleIterator.

ipc/ipc_sync_message.h

Index: ipc/ipc_sync_message.h
diff --git a/ipc/ipc_sync_message.h b/ipc/ipc_sync_message.h
index 087df0d9b5bb0254793d0685f74bda6ca2ae1872..1cc4fe55044b67c5d50063f6b7967cf4d0bdb618 100644
--- a/ipc/ipc_sync_message.h
+++ b/ipc/ipc_sync_message.h
@@ -61,7 +61,7 @@ class IPC_EXPORT SyncMessage : public Message {
 
   // Given a reply message, returns an iterator to the beginning of the data
   // (i.e. skips over the synchronous specific data).
-  static void* GetDataIterator(const Message* msg);
+  static PickleReader GetDataIterator(const Message* msg);
 
   // Given a synchronous message (or its reply), returns its id.
   static int GetMessageId(const Message& msg);
@@ -90,7 +90,8 @@ class IPC_EXPORT MessageReplyDeserializer {
  private:
   // Derived classes need to implement this, using the given iterator (which
   // is skipped past the header for synchronous messages).
-  virtual bool SerializeOutputParameters(const Message& msg, void* iter) = 0;
+  virtual bool SerializeOutputParameters(const Message& msg,
+                                         PickleReader iter) = 0;
 };
 
 // When sending a synchronous message, this structure contains an object