[generators] Store the resume mode in the generator object.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index cccbbe2896b1f6de3aa77e491735b77c200c439c..e3cb08bbc47689508f96185e4729dd83531b2ab7 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -7313,6 +7313,10 @@ class JSGeneratorObject: public JSObject {
   // [input]: The most recent input value.
   DECL_ACCESSORS(input, Object)
 
+  // [resume_mode]: The most recent resume mode.
+  enum ResumeMode { kNext, kReturn, kThrow };
+  DECL_INT_ACCESSORS(resume_mode)
+
   // [continuation]: Offset into code of continuation.
   //
   // A positive offset indicates a suspended generator.  The special
@@ -7342,13 +7346,11 @@ class JSGeneratorObject: public JSObject {
   static const int kContextOffset = kFunctionOffset + kPointerSize;
   static const int kReceiverOffset = kContextOffset + kPointerSize;
   static const int kInputOffset = kReceiverOffset + kPointerSize;
-  static const int kContinuationOffset = kInputOffset + kPointerSize;
+  static const int kResumeModeOffset = kInputOffset + kPointerSize;
+  static const int kContinuationOffset = kResumeModeOffset + kPointerSize;
   static const int kOperandStackOffset = kContinuationOffset + kPointerSize;
   static const int kSize = kOperandStackOffset + kPointerSize;
 
-  // Resume mode, for use by runtime functions.
-  enum ResumeMode { kNext, kReturn, kThrow };
-
  private:
   DISALLOW_IMPLICIT_CONSTRUCTORS(JSGeneratorObject);
 };