Move a bunch more code into the content namespace.

content/worker/worker_thread.h

Index: content/worker/worker_thread.h
===================================================================
--- content/worker/worker_thread.h	(revision 163514)
+++ content/worker/worker_thread.h	(working copy)
@@ -9,13 +9,13 @@
 
 #include "content/common/child_thread.h"
 
-class WebDatabaseObserverImpl;
 struct WorkerProcessMsg_CreateWorker_Params;
 
 namespace content {
 class AppCacheDispatcher;
 class DBMessageFilter;
 class IndexedDBMessageFilter;
+class WebDatabaseObserverImpl;
 class WebSharedWorkerStub;
 class WorkerWebKitPlatformSupportImpl;