Revert of Make sure MessagePortService is used in a thread safe manner.

content/browser/message_port_service.cc

Index: content/browser/message_port_service.cc
diff --git a/content/browser/message_port_service.cc b/content/browser/message_port_service.cc
index 9ee4d70c24490c578e3335454adb471f5249dde7..3b7ef7e5eff9047c126fb259cbf406ce3a3bdfbf 100644
--- a/content/browser/message_port_service.cc
+++ b/content/browser/message_port_service.cc
@@ -63,7 +63,7 @@
 void MessagePortService::UpdateMessagePort(int message_port_id,
                                            MessagePortDelegate* delegate,
                                            int routing_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   if (!message_ports_.count(message_port_id)) {
     NOTREACHED();
     return;
@@ -76,7 +76,6 @@
 
 void MessagePortService::OnMessagePortDelegateClosing(
     MessagePortDelegate* delegate) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
   // Check if the (possibly) crashed process had any message ports.
   for (MessagePorts::iterator iter = message_ports_.begin();
        iter != message_ports_.end();) {
@@ -90,7 +89,7 @@
 void MessagePortService::Create(int route_id,
                                 MessagePortDelegate* delegate,
                                 int* message_port_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::IO));
   *message_port_id = ++next_message_port_id_;
 
   MessagePort port;
@@ -105,7 +104,6 @@
 }
 
 void MessagePortService::Destroy(int message_port_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (!message_ports_.count(message_port_id)) {
     NOTREACHED();
     return;
@@ -118,7 +116,6 @@
 
 void MessagePortService::Entangle(int local_message_port_id,
                                   int remote_message_port_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (!message_ports_.count(local_message_port_id) ||
       !message_ports_.count(remote_message_port_id)) {
     NOTREACHED();
@@ -135,7 +132,6 @@
     int sender_message_port_id,
     const base::string16& message,
     const std::vector<int>& sent_message_port_ids) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (!message_ports_.count(sender_message_port_id)) {
     NOTREACHED();
     return;
@@ -199,7 +195,6 @@
 }
 
 void MessagePortService::QueueMessages(int message_port_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (!message_ports_.count(message_port_id)) {
     NOTREACHED();
     return;
@@ -216,7 +211,6 @@
 void MessagePortService::SendQueuedMessages(
     int message_port_id,
     const QueuedMessages& queued_messages) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (!message_ports_.count(message_port_id)) {
     NOTREACHED();
     return;
@@ -246,7 +240,6 @@
 }
 
 void MessagePortService::SendQueuedMessagesIfPossible(int message_port_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (!message_ports_.count(message_port_id)) {
     NOTREACHED();
     return;
@@ -264,7 +257,6 @@
 }
 
 void MessagePortService::HoldMessages(int message_port_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (!message_ports_.count(message_port_id)) {
     NOTREACHED();
     return;
@@ -279,7 +271,6 @@
 }
 
 void MessagePortService::ClosePort(int message_port_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (!message_ports_.count(message_port_id)) {
     NOTREACHED();
     return;
@@ -299,7 +290,6 @@
 }
 
 void MessagePortService::ReleaseMessages(int message_port_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (!message_ports_.count(message_port_id)) {
     NOTREACHED();
     return;