[runtime] Introduce dedicated JSBoundFunction to represent bound functions.

src/objects-debug.cc

Index: src/objects-debug.cc
diff --git a/src/objects-debug.cc b/src/objects-debug.cc
index a05d1e703626b125635e9ce15ea935164545023d..1115a5e4164d3ae47ea1cc30645fa784ca0224d3 100644
--- a/src/objects-debug.cc
+++ b/src/objects-debug.cc
@@ -114,6 +114,9 @@ void HeapObject::HeapObjectVerify() {
     case JS_DATE_TYPE:
       JSDate::cast(this)->JSDateVerify();
       break;
+    case JS_BOUND_FUNCTION_TYPE:
+      JSBoundFunction::cast(this)->JSBoundFunctionVerify();
+      break;
     case JS_FUNCTION_TYPE:
       JSFunction::cast(this)->JSFunctionVerify();
       break;
@@ -542,6 +545,21 @@ void SlicedString::SlicedStringVerify() {
 }
 
 
+void JSBoundFunction::JSBoundFunctionVerify() {
+  CHECK(IsJSBoundFunction());
+  VerifyObjectField(kLengthOffset);
+  VerifyObjectField(kNameOffset);
+  VerifyObjectField(kBoundThisOffset);
+  VerifyObjectField(kBoundTargetFunctionOffset);
+  VerifyObjectField(kBoundArgumentsOffset);
+  VerifyObjectField(kCreationContextOffset);
+  CHECK(bound_target_function()->IsCallable());
+  CHECK(creation_context()->IsNativeContext());
+  CHECK(IsCallable());
+  CHECK_EQ(IsConstructor(), bound_target_function()->IsConstructor());
+}
+
+
 void JSFunction::JSFunctionVerify() {
   CHECK(IsJSFunction());
   VerifyObjectField(kPrototypeOrInitialMapOffset);