CFXJS_Engine::GetObjDefnID is a static method

So call it as such.  Fix two places where we're invoking it off
of an intance.

Change-Id: I08712fa27dbdf85c9195cedcc62d7d741b0ad091
Reviewed-on: https://pdfium-review.googlesource.com/6110
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/fpdfsdk/javascript/Document.cpp b/fpdfsdk/javascript/Document.cpp
index a760ad9..5d5c2b5 100644
--- a/fpdfsdk/javascript/Document.cpp
+++ b/fpdfsdk/javascript/Document.cpp
@@ -1211,7 +1211,7 @@
   }
 
   v8::Local<v8::Object> pJSIcon = params[1].ToV8Object(pRuntime);
-  if (pRuntime->GetObjDefnID(pJSIcon) != CJS_Icon::g_nObjDefnID) {
+  if (CFXJS_Engine::GetObjDefnID(pJSIcon) != CJS_Icon::g_nObjDefnID) {
     sError = JSGetStringFromID(IDS_STRING_JSTYPEERROR);
     return false;
   }