Merge to XFA: Pass IJS_Runtime, not IJS_Context, to native object constructors.

Original Review URL: https://codereview.chromium.org/1389163007 .
(cherry picked from commit 848a13b6777cbff8cc4aea3ab3d69eaa0b82ae6c)

Merge conflics in:
fpdfsdk/src/javascript/JS_Runtime.cpp
fpdfsdk/src/javascript/JS_Runtime_Stub.cpp
fpdfsdk/src/jsapi/fxjs_v8.cpp

R=thestig@chromium.org

Review URL: https://codereview.chromium.org/1394993006 .
diff --git a/fpdfsdk/src/javascript/JS_Runtime.h b/fpdfsdk/src/javascript/JS_Runtime.h
index c259a41..4772823 100644
--- a/fpdfsdk/src/javascript/JS_Runtime.h
+++ b/fpdfsdk/src/javascript/JS_Runtime.h
@@ -40,6 +40,9 @@
   IJS_Context* GetCurrentContext() override;
   void SetReaderDocument(CPDFSDK_Document* pReaderDoc) override;
   CPDFSDK_Document* GetReaderDocument() override { return m_pDocument; }
+  int Execute(IJS_Context* cc,
+              const wchar_t* script,
+              CFX_WideString* info) override;
 
   CPDFDoc_Environment* GetReaderApp() const { return m_pApp; }