Revert 189518 "PPAPI: Remove threading options; it's always on"

trunk/src/webkit/plugins/ppapi/host_var_tracker.cc

Index: trunk/src/webkit/plugins/ppapi/host_var_tracker.cc
===================================================================
--- trunk/src/webkit/plugins/ppapi/host_var_tracker.cc	(revision 189681)
+++ trunk/src/webkit/plugins/ppapi/host_var_tracker.cc	(working copy)
@@ -16,9 +16,7 @@
 namespace webkit {
 namespace ppapi {
 
-HostVarTracker::HostVarTracker()
-  : VarTracker(SINGLE_THREADED),
-    last_shared_memory_map_id_(0) {
+HostVarTracker::HostVarTracker() : last_shared_memory_map_id_(0) {
 }
 
 HostVarTracker::~HostVarTracker() {
@@ -35,7 +33,7 @@
 }
 
 void HostVarTracker::AddNPObjectVar(NPObjectVar* object_var) {
-  CheckThreadingPreconditions();
+  DCHECK(CalledOnValidThread());
 
   InstanceMap::iterator found_instance = instance_map_.find(
       object_var->pp_instance());
@@ -55,7 +53,7 @@
 }
 
 void HostVarTracker::RemoveNPObjectVar(NPObjectVar* object_var) {
-  CheckThreadingPreconditions();
+  DCHECK(CalledOnValidThread());
 
   InstanceMap::iterator found_instance = instance_map_.find(
       object_var->pp_instance());
@@ -80,7 +78,7 @@
 
 NPObjectVar* HostVarTracker::NPObjectVarForNPObject(PP_Instance instance,
                                                     NPObject* np_object) {
-  CheckThreadingPreconditions();
+  DCHECK(CalledOnValidThread());
 
   InstanceMap::iterator found_instance = instance_map_.find(instance);
   if (found_instance == instance_map_.end())
@@ -95,7 +93,7 @@
 }
 
 int HostVarTracker::GetLiveNPObjectVarsForInstance(PP_Instance instance) const {
-  CheckThreadingPreconditions();
+  DCHECK(CalledOnValidThread());
 
   InstanceMap::const_iterator found = instance_map_.find(instance);
   if (found == instance_map_.end())
@@ -104,7 +102,7 @@
 }
 
 void HostVarTracker::DidDeleteInstance(PP_Instance instance) {
-  CheckThreadingPreconditions();
+  DCHECK(CalledOnValidThread());
 
   InstanceMap::iterator found_instance = instance_map_.find(instance);
   if (found_instance == instance_map_.end())