Pass v8::Isolate to PDFium at init time.

fpdfsdk/include/jsapi/fxjs_v8.h

Index: fpdfsdk/include/jsapi/fxjs_v8.h
diff --git a/fpdfsdk/include/jsapi/fxjs_v8.h b/fpdfsdk/include/jsapi/fxjs_v8.h
index 60fcea63410f660b5f8f2844e3fa5125194606a4..1705b894cf3b9ede31aa21c759f86b7376be5c30 100644
--- a/fpdfsdk/include/jsapi/fxjs_v8.h
+++ b/fpdfsdk/include/jsapi/fxjs_v8.h
@@ -62,9 +62,14 @@ using FXJS_CONSTRUCTOR = void (*)(IFXJS_Context* cc,
 using FXJS_DESTRUCTOR = void (*)(v8::Local<v8::Object> obj);
 
 // Call before making FXJS_PrepareIsolate call.
-void FXJS_Initialize(unsigned int embedderDataSlot);
+void FXJS_Initialize(unsigned int embedderDataSlot, v8::Isolate* pIsolate);
 void FXJS_Release();
 
+// Gets the global isolate set by FXJS_Initialize(), or makes a new one each
+// time if there is no such isolate. Returns true if a new isolate had to be
+// created.
+bool FXJS_GetIsolate(v8::Isolate** pResultIsolate);
+
 // Call before making FXJS_Define* calls. Resources allocated here are cleared
 // as part of FXJS_ReleaseRuntime().
 void FXJS_PrepareIsolate(v8::Isolate* pIsolate);