PPAPI: Make CompletionCallbacks work right on background threads.

ppapi/shared_impl/ppapi_globals.h

Index: ppapi/shared_impl/ppapi_globals.h
diff --git a/ppapi/shared_impl/ppapi_globals.h b/ppapi/shared_impl/ppapi_globals.h
index e95cf48b2392def80cbf9ab4b59b130b54ebe9df..b03d35c9bd87de5b19b45ac1fc0a1e28a50c9fab 100644
--- a/ppapi/shared_impl/ppapi_globals.h
+++ b/ppapi/shared_impl/ppapi_globals.h
@@ -24,6 +24,7 @@ class MessageLoopProxy;
 namespace ppapi {
 
 class CallbackTracker;
+class MessageLoopShared;
 class ResourceTracker;
 class VarTracker;
 
@@ -35,6 +36,7 @@ class ResourceCreationAPI;
 // Abstract base class
 class PPAPI_SHARED_EXPORT PpapiGlobals {
  public:
+  // Must be created on the main thread.
   PpapiGlobals();
 
   // This constructor is to be used only for making a PpapiGlobal for testing
@@ -42,7 +44,7 @@ class PPAPI_SHARED_EXPORT PpapiGlobals {
   // tests that use this feature, the "test" PpapiGlobals should be constructed
   // using this method. See SetPpapiGlobalsOnThreadForTest for more information.
   struct ForTest {};
-  PpapiGlobals(ForTest);
+  explicit PpapiGlobals(ForTest);
 
   virtual ~PpapiGlobals();
 
@@ -71,6 +73,7 @@ class PPAPI_SHARED_EXPORT PpapiGlobals {
   virtual VarTracker* GetVarTracker() = 0;
   virtual CallbackTracker* GetCallbackTrackerForInstance(
       PP_Instance instance) = 0;
+
   virtual base::Lock* GetProxyLock() = 0;
 
   // Logs the given string to the JS console. If "source" is empty, the name of
@@ -103,11 +106,15 @@ class PPAPI_SHARED_EXPORT PpapiGlobals {
   // failure.
   virtual PP_Module GetModuleForInstance(PP_Instance instance) = 0;
 
-  // Returns the base::MessageLoopProxy for the main thread. Note that this must
-  // be called on the main thread the first time so that it can initialize
-  // its static data.
+  // Returns the base::MessageLoopProxy for the main thread. This is set in the
+  // constructor, so PpapiGlobals must be created on the main thread.
   base::MessageLoopProxy* GetMainThreadMessageLoop();
 
+  // Return the MessageLoopShared of the current thread, if any. This will
+  // always return NULL on the host side, where PPB_MessageLoop is not
+  // supported.
+  virtual MessageLoopShared* GetCurrentMessageLoop() = 0;
+
   // Returns the command line for the process.
   virtual std::string GetCmdLine() = 0;
 
@@ -127,7 +134,7 @@ class PPAPI_SHARED_EXPORT PpapiGlobals {
 
   static PpapiGlobals* ppapi_globals_;
 
-  scoped_refptr<base::MessageLoopProxy> message_loop_proxy_;
+  scoped_refptr<base::MessageLoopProxy> main_loop_proxy_;
 
   DISALLOW_COPY_AND_ASSIGN(PpapiGlobals);
 };