Plumb in an externally created v8::Isolate

public/fpdf_formfill.h

Index: public/fpdf_formfill.h
diff --git a/public/fpdf_formfill.h b/public/fpdf_formfill.h
index a1b9ec2a775e03b25659c2c45a262c65c39578f6..1cc5551e0bae45768826f9772efa7660701a7a84 100644
--- a/public/fpdf_formfill.h
+++ b/public/fpdf_formfill.h
@@ -18,11 +18,13 @@ extern "C" {
 
 typedef struct _IPDF_JsPlatform
 {
-/**
-* Version number of the interface. Currently must be 1.
+    /**
+    * Version number of the interface. Currently must be 2.
     **/
     int version;
 
+    /* Version 1. */
+
     /**
     * Method: app_alert
     *           pop up a dialog to show warning or hint.
@@ -222,6 +224,13 @@ typedef struct _IPDF_JsPlatform
     *   pointer to FPDF_FORMFILLINFO interface.
     **/
     void*   m_pFormfillinfo;
+
+    /* Version 2. */
+
+    /**
+    *   pointer to the v8::Isolate to use, or NULL to force PDFium to create one.
+    **/
+    void*   m_isolate;
 } IPDF_JSPLATFORM;
 
 // Flags for Cursor type