Fix unit test to allow repeated successful runs by avoiding a function static variable in tests.

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 00fb9b16e12ef8e1f9151dca5172a71866fd4ab4..b519b4ed06d580bbe011d151d57ac7fcaef95db2 100644
--- a/ppapi/shared_impl/ppapi_globals.h
+++ b/ppapi/shared_impl/ppapi_globals.h
@@ -105,7 +105,8 @@ class PPAPI_SHARED_EXPORT PpapiGlobals {
   // 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.
-  base::MessageLoopProxy* GetMainThreadMessageLoop();
+  // Virtual for testing.
+  virtual base::MessageLoopProxy* GetMainThreadMessageLoop();
 
   // Returns the command line for the process.
   virtual std::string GetCmdLine() = 0;