[generators] Implement %GeneratorGetSourcePosition.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index a7aabe23e0f856b18734e09f3fe4f40c7b4b508d..f76e1d7fb2008abd2a344bae25c19d92e0415a1b 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -7363,23 +7363,32 @@ 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)
+  // [input_or_debug_pos]
+  // For executing generators: the most recent input value.
+  // For suspended new-style generators: debug information (bytecode offset).
+  // For suspended old-style generators: unused.
+  // There is currently no need to remember the most recent input value for a
+  // suspended generator.
+  DECL_ACCESSORS(input_or_debug_pos, Object)
 
   // [resume_mode]: The most recent resume mode.
   enum ResumeMode { kNext, kReturn, kThrow };
   DECL_INT_ACCESSORS(resume_mode)
 
-  // [continuation]: Offset into code of continuation.
+  // [continuation]
   //
-  // A positive offset indicates a suspended generator.  The special
+  // A positive value indicates a suspended generator.  The special
   // kGeneratorExecuting and kGeneratorClosed values indicate that a generator
   // cannot be resumed.
   inline int continuation() const;
   inline void set_continuation(int continuation);
-  inline bool is_closed();
-  inline bool is_executing();
-  inline bool is_suspended();
+  inline bool is_closed() const;
+  inline bool is_executing() const;
+  inline bool is_suspended() const;
+
+  // For suspended generators: the source position at which the generator
+  // is suspended.
+  int source_position() const;
 
   // [operand_stack]: Saved operand stack.
   DECL_ACCESSORS(operand_stack, FixedArray)
@@ -7397,8 +7406,8 @@ 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 kInputOffset = kReceiverOffset + kPointerSize;
-  static const int kResumeModeOffset = kInputOffset + kPointerSize;
+  static const int kInputOrDebugPosOffset = kReceiverOffset + kPointerSize;
+  static const int kResumeModeOffset = kInputOrDebugPosOffset + kPointerSize;
   static const int kContinuationOffset = kResumeModeOffset + kPointerSize;
   static const int kOperandStackOffset = kContinuationOffset + kPointerSize;
   static const int kSize = kOperandStackOffset + kPointerSize;