Add ref count to service workers for extension API.

extensions/common/extension_messages.h

Index: extensions/common/extension_messages.h
diff --git a/extensions/common/extension_messages.h b/extensions/common/extension_messages.h
index f9e9bcb31674e66f6c73de539f2194795d7689aa..0a0b1c2ae6d28bbef2d3f4dec5c0af79aeb7cbe3 100644
--- a/extensions/common/extension_messages.h
+++ b/extensions/common/extension_messages.h
@@ -116,9 +116,9 @@ IPC_STRUCT_BEGIN(ExtensionHostMsg_Request_Params)
   // id. Otherwise, this is -1.
   IPC_STRUCT_MEMBER(int, worker_thread_id)
 
-  // If this API call is for a service worker, then this is the embedded
-  // worker id. Otherwise, this is -1.
-  IPC_STRUCT_MEMBER(int, embedded_worker_id)
+  // If this API call is for a service worker, then this is the service
+  // worker version id. Otherwise, this is -1.
+  IPC_STRUCT_MEMBER(int64_t, service_worker_version_id)
 IPC_STRUCT_END()
 
 // Allows an extension to execute code in a tab.
@@ -887,3 +887,15 @@ IPC_MESSAGE_CONTROL5(ExtensionMsg_ResponseWorker,
                      bool /* success */,
                      base::ListValue /* response wrapper (see comment above) */,
                      std::string /* error */)
+
+// Asks the browser to increment the pending activity count for

[Tom Sepez, 2016/10/07 22:31:46]

What happens browser-side if a compromised renderer sends more decrements than
increments, or continues to use in some manner a worker that has been
decremented to 0?

[lazyboy, 2016/10/07 23:16:59]

This is expected to be unique, I've added a comment saying that.

A compromised renderer can keep sending same request_uuid, in that case:
For increment: if there's any request that was already pending with
|request_uuid|, browser will ignore it (I've not been doing that, added that in
latest patch, thanks).
For decrement: It will only work if browser has a pending request with
|request_uuid|, otherwise it will ignore the request.

+// the worker with version id |service_worker_version_id|.
+IPC_MESSAGE_CONTROL2(ExtensionHostMsg_IncrementServiceWorkerActivity,
+                     int64_t /* service_worker_version_id */,
+                     std::string /* request_uuid */)
+
+// Asks the browser to decrement the pending activity count for
+// the worker with version id |service_worker_version_id|.
+IPC_MESSAGE_CONTROL2(ExtensionHostMsg_DecrementServiceWorkerActivity,
+                     int64_t /* service_worker_version_id */,
+                     std::string /* request_uuid */)