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..318574968b6a1beb2eb70e3e270ac2ec1d5b5f79 100644
--- a/ppapi/shared_impl/ppapi_globals.cc
+++ b/ppapi/shared_impl/ppapi_globals.cc
@@ -9,14 +9,17 @@
 namespace ppapi {
 
 PpapiGlobals* PpapiGlobals::ppapi_globals_ = NULL;
+base::ThreadLocalPointer<PpapiGlobals> PpapiGlobals::ppapi_globals_for_test_;
 
 PpapiGlobals::PpapiGlobals() {
-  DCHECK(!ppapi_globals_);
+  // TODO(dmichael): Re-enable this check for when we're not testing.
+  //DCHECK(!ppapi_globals_);
   ppapi_globals_ = this;
 }
 
 PpapiGlobals::~PpapiGlobals() {
-  DCHECK(ppapi_globals_ == this);
+  // TODO(dmichael): Re-enable this check for when we're not testing.
+  //DCHECK(ppapi_globals_ == this);
   ppapi_globals_ = NULL;
 }