[runtime] Introduce dedicated JSBoundFunction to represent bound functions.

src/full-codegen/x64/full-codegen-x64.cc

Index: src/full-codegen/x64/full-codegen-x64.cc
diff --git a/src/full-codegen/x64/full-codegen-x64.cc b/src/full-codegen/x64/full-codegen-x64.cc
index 1cc18044fd298189403d1b54d6c3c3de6d49f9e4..88b37a30a08b08049a28372714efb1e80f98de7f 100644
--- a/src/full-codegen/x64/full-codegen-x64.cc
+++ b/src/full-codegen/x64/full-codegen-x64.cc
@@ -3020,9 +3020,9 @@ void FullCodeGenerator::EmitIsFunction(CallRuntime* expr) {
                          &if_true, &if_false, &fall_through);
 
   __ JumpIfSmi(rax, if_false);
-  __ CmpObjectType(rax, JS_FUNCTION_TYPE, rbx);
+  __ CmpObjectType(rax, FIRST_FUNCTION_TYPE, rbx);
   PrepareForBailoutBeforeSplit(expr, true, if_true, if_false);
-  Split(equal, if_true, if_false, fall_through);
+  Split(above_equal, if_true, if_false, fall_through);
 
   context()->Plug(if_true, if_false);
 }