Refactor Pickle Read methods to use higher performance PickleIterator.

ipc/ipc_sync_message.cc

Index: ipc/ipc_sync_message.cc
diff --git a/ipc/ipc_sync_message.cc b/ipc/ipc_sync_message.cc
index 875f97b1fec167162f83a5919f7fe8e4cf91b534..02ce8b2079684f439447fe4055ac1e62311711df 100644
--- a/ipc/ipc_sync_message.cc
+++ b/ipc/ipc_sync_message.cc
@@ -74,8 +74,8 @@ bool SyncMessage::IsMessageReplyTo(const Message& msg, int request_id) {
   return GetMessageId(msg) == request_id;
 }
 
-void* SyncMessage::GetDataIterator(const Message* msg) {
-  void* iter = const_cast<char*>(msg->payload());
+PickleReader SyncMessage::GetDataIterator(const Message* msg) {
+  PickleReader iter(*msg);
   UpdateIter(&iter, kSyncMessageHeaderSize);
   return iter;
 }
@@ -110,7 +110,7 @@ Message* SyncMessage::GenerateReply(const Message* msg) {
 bool SyncMessage::ReadSyncHeader(const Message& msg, SyncHeader* header) {
   DCHECK(msg.is_sync() || msg.is_reply());
 
-  void* iter = NULL;
+  PickleReader iter(msg);
   bool result = msg.ReadInt(&iter, &header->message_id);
   if (!result) {
     NOTREACHED();