Make it possible to have 1 PpapiGlobals per thread. Update unit tests.

ppapi/shared_impl/ppapi_globals.cc

Index: ppapi/shared_impl/ppapi_globals.cc
diff --git a/ppapi/shared_impl/ppapi_globals.cc b/ppapi/shared_impl/ppapi_globals.cc
index 9b5e9a82cb3fede21d10ab13b46f095acb127d8f..3e71bb388b5a79f6bd3d992989638658b2389e77 100644
--- a/ppapi/shared_impl/ppapi_globals.cc
+++ b/ppapi/shared_impl/ppapi_globals.cc
@@ -9,15 +9,28 @@
 namespace ppapi {
 
 PpapiGlobals* PpapiGlobals::ppapi_globals_ = NULL;
+base::ThreadLocalPointer<PpapiGlobals> PpapiGlobals::ppapi_globals_for_test_;
 
 PpapiGlobals::PpapiGlobals() {
   DCHECK(!ppapi_globals_);
   ppapi_globals_ = this;
 }
 
+PpapiGlobals::PpapiGlobals(ForTest) {
+  DCHECK(!ppapi_globals_);
+}
+
 PpapiGlobals::~PpapiGlobals() {
-  DCHECK(ppapi_globals_ == this);
+  DCHECK(ppapi_globals_ == this || !ppapi_globals_);
   ppapi_globals_ = NULL;
 }
 
+// static
+void PpapiGlobals::SetPpapiGlobalsOnThreadForTest(PpapiGlobals* ptr) {
+  // If we're using a per-thread PpapiGlobals, we should not have a global one.
+  // If we allowed it, it would always over-ride the "test" versions.
+  DCHECK(!ppapi_globals_);
+  ppapi_globals_for_test_.Set(ptr);
+}
+
 }  // namespace ppapi