Revert 187427 "PPAPI: Remove threading options; it's always on"

ppapi/shared_impl/resource_tracker.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef PPAPI_SHARED_IMPL_RESOURCE_TRACKER_H_
 #define PPAPI_SHARED_IMPL_RESOURCE_TRACKER_H_
 
 #include <set>
 
 #include "base/basictypes.h"
 #include "base/hash_tables.h"
 #include "base/memory/linked_ptr.h"
-#include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "base/threading/thread_checker_impl.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_resource.h"
 #include "ppapi/shared_impl/ppapi_shared_export.h"
 
 namespace ppapi {
 
 class Resource;
 
 class PPAPI_SHARED_EXPORT ResourceTracker {
  public:
-  // A SINGLE_THREADED ResourceTracker will use a thread-checker to make sure
-  // it's always invoked on the same thread on which it was constructed. A
-  // THREAD_SAFE ResourceTracker will check that the ProxyLock is held. See
-  // CheckThreadingPreconditions() for more details.
-  enum ThreadMode { SINGLE_THREADED, THREAD_SAFE };
-  explicit ResourceTracker(ThreadMode thread_mode);
+  ResourceTracker();
   virtual ~ResourceTracker();
 
   // The returned pointer will be NULL if there is no resource. The reference
   // count of the resource is unaffected.
   Resource* GetResource(PP_Resource res) const;
 
   void AddRefResource(PP_Resource res);
   void ReleaseResource(PP_Resource res);
 
   // Releases a reference on the given resource once the message loop returns.
   void ReleaseResourceSoon(PP_Resource res);
 
   // Notifies the tracker that a new instance has been created. This must be
   // called before creating any resources associated with the instance.
   void DidCreateInstance(PP_Instance instance);
 
   // Called when an instance is being deleted. All plugin refs for the
   // associated resources will be force freed, and the resources (if they still
   // exist) will be disassociated from the instance.
   void DidDeleteInstance(PP_Instance instance);
 
   // Returns the number of resources associated with the given instance.
   // Returns 0 if the instance isn't known.
   int GetLiveObjectsForInstance(PP_Instance instance) const;
 
  protected:
   // This calls AddResource and RemoveResource.
   friend class Resource;
 
-  // On the host-side, make sure we are called on the right thread. On the
-  // plugin side, make sure we have the proxy lock.
-  void CheckThreadingPreconditions() const;
-
   // Adds the given resource to the tracker, associating it with the instance
   // stored in the resource object. The new resource ID is returned, and the
   // resource will have 0 plugin refcount. This is called by the resource
   // constructor.
   //
   // Returns 0 if the resource could not be added.
   virtual PP_Resource AddResource(Resource* object);
 
   // The opposite of AddResource, this removes the tracking information for
   // the given resource. It's called from the resource destructor.
@@ skipping 25 matching lines @@
   //
   // A resource will be in this list as long as the object is alive.
   typedef std::pair<Resource*, int> ResourceAndRefCount;
   typedef base::hash_map<PP_Resource, ResourceAndRefCount> ResourceMap;
   ResourceMap live_resources_;
 
   int32 last_resource_value_;
 
   base::WeakPtrFactory<ResourceTracker> weak_ptr_factory_;
 
-  // On the host side, we want to check that we are only called on the main
-  // thread. This is to protect us from accidentally using the tracker from
-  // other threads (especially the IO thread). On the plugin side, the tracker
-  // is protected by the proxy lock and is thread-safe, so this will be NULL.
-  scoped_ptr<base::ThreadChecker> thread_checker_;
+  // TODO(raymes): We won't need to do thread checks once pepper calls are
+  // allowed off of the main thread.
+  // See http://code.google.com/p/chromium/issues/detail?id=92909.
+#ifdef ENABLE_PEPPER_THREADING
+  base::ThreadCheckerDoNothing thread_checker_;
+#else
+  // TODO(raymes): We've seen plugins (Flash) creating resources from random
+  // threads. Let's always crash for now in this case. Once we have a handle
+  // over how common this is, we can change ThreadCheckerImpl->ThreadChecker
+  // so that we only crash in debug mode. See
+  // https://code.google.com/p/chromium/issues/detail?id=146415.
+  base::ThreadCheckerImpl thread_checker_;
+#endif
 
   DISALLOW_COPY_AND_ASSIGN(ResourceTracker);
 };
 
 }  // namespace ppapi
 
 #endif  // PPAPI_SHARED_IMPL_RESOURCE_TRACKER_H_