Implement the function.sent proposal.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 71bbbce442f6c6e36fd078c6e04c58acdaaad396..e138571caeeaa8891f28c0a4aff3cf6f0041a54a 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -7203,6 +7203,9 @@ class JSGeneratorObject: public JSObject {
   // [receiver]: The receiver of the suspended computation.
   DECL_ACCESSORS(receiver, Object)
 
+  // [input]: The most recent input value.
+  DECL_ACCESSORS(input, Object)
+
   // [continuation]: Offset into code of continuation.
   //
   // A positive offset indicates a suspended generator.  The special
@@ -7231,7 +7234,8 @@ class JSGeneratorObject: public JSObject {
   static const int kFunctionOffset = JSObject::kHeaderSize;
   static const int kContextOffset = kFunctionOffset + kPointerSize;
   static const int kReceiverOffset = kContextOffset + kPointerSize;
-  static const int kContinuationOffset = kReceiverOffset + kPointerSize;
+  static const int kInputOffset = kReceiverOffset + kPointerSize;
+  static const int kContinuationOffset = kInputOffset + kPointerSize;
   static const int kOperandStackOffset = kContinuationOffset + kPointerSize;
   static const int kSize = kOperandStackOffset + kPointerSize;