Add CHECKs to ensure that PPAPI resources are created on the right thread

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/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:
@@ skipping 32 matching lines @@
   // 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.
   virtual void RemoveResource(Resource* object);
 
+ private:
   // Calls LastPluginRefWasDeleted on the given resource object and cancels
   // pending callbacks for the resource.
   void LastPluginRefWasDeleted(Resource* object);
 
- private:
   typedef std::set<PP_Resource> ResourceSet;
 
   struct InstanceData {
     // Lists all resources associated with the given instance as non-owning
     // pointers. This allows us to notify those resources that the instance is
     // going away (otherwise, they may crash if they outlive the instance).
     ResourceSet resources;
   };
   typedef base::hash_map<PP_Instance, linked_ptr<InstanceData> > InstanceMap;
 
   InstanceMap instance_map_;
 
   // For each PP_Resource, keep the object pointer and a plugin use count.
   // This use count is different then Resource object's RefCount, and is
   // manipulated using this AddRefResource/UnrefResource. When the plugin use
   // count is positive, we keep an extra ref on the Resource on
   // behalf of the plugin. When it drops to 0, we free that ref, keeping
   // the resource in the list.
   //
   // 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_;
 
+  // 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_