Merge to XFA: Only call DefineJSObjects() once for the global V8 isolate.

BUG=539106
TBR=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1386823002 .

(cherry picked from commit 7dfe5929282cb6d78d7b5e32e1d72e9db99d3066)

Review URL: https://codereview.chromium.org/1400503003 .
diff --git a/fpdfsdk/src/javascript/JS_Runtime.cpp b/fpdfsdk/src/javascript/JS_Runtime.cpp
index f97b454..a449a14 100644
--- a/fpdfsdk/src/javascript/JS_Runtime.cpp
+++ b/fpdfsdk/src/javascript/JS_Runtime.cpp
@@ -70,7 +70,9 @@
     return;
   }
 
-  DefineJSObjects();
+  if (m_isolateManaged || FXJS_GlobalIsolateRefCount() == 0)
+    DefineJSObjects();
+
   CPDFXFA_App::GetInstance()->SetJavaScriptInitialized(TRUE);
 
   CJS_Context* pContext = (CJS_Context*)NewContext();