Avoid accessing VarTracker from multiple threads.

ppapi/proxy/plugin_var_tracker.cc

 // 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.
 
 #include "ppapi/proxy/plugin_var_tracker.h"
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/singleton.h"
 #include "ppapi/c/ppb_var.h"
 #include "ppapi/proxy/plugin_array_buffer_var.h"
@@ skipping 20 matching lines @@
 }
 
 PluginVarTracker::PluginVarTracker() {
 }
 
 PluginVarTracker::~PluginVarTracker() {
 }
 
 PP_Var PluginVarTracker::ReceiveObjectPassRef(const PP_Var& host_var,
                                               PluginDispatcher* dispatcher) {
+  DCHECK(CalledOnValidThread());
   DCHECK(host_var.type == PP_VARTYPE_OBJECT);
 
   // Get the object.
   scoped_refptr<ProxyObjectVar> object(
       FindOrMakePluginVarFromHostVar(host_var, dispatcher));
 
   // Actually create the PP_Var, this will add all the tracking info but not
   // adjust any refcounts.
   PP_Var ret = GetOrCreateObjectVarID(object.get());
 
   VarInfo& info = GetLiveVar(ret)->second;
   if (info.ref_count > 0) {
     // We already had a reference to it before. That means the renderer now has
     // two references on our behalf. We want to transfer that extra reference
     // to our list. This means we addref in the plugin, and release the extra
     // one in the renderer.
     SendReleaseObjectMsg(*object);
   }
   info.ref_count++;
   return ret;
 }
 
 PP_Var PluginVarTracker::TrackObjectWithNoReference(
     const PP_Var& host_var,
     PluginDispatcher* dispatcher) {
+  DCHECK(CalledOnValidThread());
   DCHECK(host_var.type == PP_VARTYPE_OBJECT);
 
   // Get the object.
   scoped_refptr<ProxyObjectVar> object(
       FindOrMakePluginVarFromHostVar(host_var, dispatcher));
 
   // Actually create the PP_Var, this will add all the tracking info but not
   // adjust any refcounts.
   PP_Var ret = GetOrCreateObjectVarID(object.get());
 
   VarInfo& info = GetLiveVar(ret)->second;
   info.track_with_no_reference_count++;
   return ret;
 }
 
 void PluginVarTracker::StopTrackingObjectWithNoReference(
     const PP_Var& plugin_var) {
+  DCHECK(CalledOnValidThread());
   DCHECK(plugin_var.type == PP_VARTYPE_OBJECT);
+
   VarMap::iterator found = GetLiveVar(plugin_var);
   if (found == live_vars_.end()) {
     NOTREACHED();
     return;
   }
 
   DCHECK(found->second.track_with_no_reference_count > 0);
   found->second.track_with_no_reference_count--;
   DeleteObjectInfoIfNecessary(found);
 }
 
 PP_Var PluginVarTracker::GetHostObject(const PP_Var& plugin_object) const {
+  DCHECK(CalledOnValidThread());
+
   if (plugin_object.type != PP_VARTYPE_OBJECT) {
     NOTREACHED();
     return PP_MakeUndefined();
   }
 
   Var* var = GetVar(plugin_object);
   ProxyObjectVar* object = var->AsProxyObjectVar();
   if (!object) {
     NOTREACHED();
     return PP_MakeUndefined();
   }
 
   // Make a var with the host ID.
   PP_Var ret = { PP_VARTYPE_OBJECT };
   ret.value.as_id = object->host_var_id();
   return ret;
 }
 
 PluginDispatcher* PluginVarTracker::DispatcherForPluginObject(
     const PP_Var& plugin_object) const {
+  DCHECK(CalledOnValidThread());
+
   if (plugin_object.type != PP_VARTYPE_OBJECT)
     return NULL;
 
   VarMap::const_iterator found = GetLiveVar(plugin_object);
   if (found == live_vars_.end())
     return NULL;
 
   ProxyObjectVar* object = found->second.var->AsProxyObjectVar();
   if (!object)
     return NULL;
   return object->dispatcher();
 }
 
 void PluginVarTracker::ReleaseHostObject(PluginDispatcher* dispatcher,
                                          const PP_Var& host_object) {
+  DCHECK(CalledOnValidThread());
+  DCHECK(host_object.type == PP_VARTYPE_OBJECT);
+
   // Convert the host object to a normal var valid in the plugin.
-  DCHECK(host_object.type == PP_VARTYPE_OBJECT);
   HostVarToPluginVarMap::iterator found = host_var_to_plugin_var_.find(
       HostVar(dispatcher, static_cast<int32>(host_object.value.as_id)));
   if (found == host_var_to_plugin_var_.end()) {
     NOTREACHED();
     return;
   }
 
   // Now just release the object given the plugin var ID.
   ReleaseVar(found->second);
 }
@@ skipping 112 matching lines @@
   VarMap::iterator ret = live_vars_.find(found->second);
   DCHECK(ret != live_vars_.end());
 
   // All objects should be proxy objects.
   DCHECK(ret->second.var->AsProxyObjectVar());
   return scoped_refptr<ProxyObjectVar>(ret->second.var->AsProxyObjectVar());
 }
 
 }  // namesace proxy
 }  // namespace ppapi