Make it possible to have 1 PpapiGlobals per thread. Update unit 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 b3d7d555514785a41f57891eb5ec872c04427c78..cdbe39faf2dc95a51204ce0b98476b174c72644b 100644
--- a/ppapi/shared_impl/ppapi_globals.h
+++ b/ppapi/shared_impl/ppapi_globals.h
@@ -6,6 +6,7 @@
 #define PPAPI_SHARED_IMPL_PPAPI_GLOBALS_H_
 
 #include "base/basictypes.h"
+#include "base/threading/thread_local.h"  // For testing purposes only.
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_module.h"
 #include "ppapi/shared_impl/api_id.h"
@@ -25,7 +26,15 @@ class PPAPI_SHARED_EXPORT PpapiGlobals {
   virtual ~PpapiGlobals();
 
   // Getter for the global singleton.
-  inline static PpapiGlobals* Get() { return ppapi_globals_; }
+  inline static PpapiGlobals* Get() {
+    if (ppapi_globals_)
+      return ppapi_globals_;
+    return ppapi_globals_for_test_.Get();
+  }
+  static void SetPpapiGlobalsForTest(PpapiGlobals* ptr) {
+    ppapi_globals_for_test_.Set(ptr);
+    ppapi_globals_ = NULL;
+  }
 
   // Retrieves the corresponding tracker.
   virtual ResourceTracker* GetResourceTracker() = 0;
@@ -43,6 +52,7 @@ class PPAPI_SHARED_EXPORT PpapiGlobals {
 
  private:
   static PpapiGlobals* ppapi_globals_;
+  static base::ThreadLocalPointer<PpapiGlobals> ppapi_globals_for_test_;
 
   DISALLOW_COPY_AND_ASSIGN(PpapiGlobals);
 };