Reimplement Function.prototype.bind.

src/runtime.js

Index: src/runtime.js
diff --git a/src/runtime.js b/src/runtime.js
index a12f6c7b093cb6302b363944d47239c80d4a1055..c3554c63723919a27c9d03dff017b1ab0f4fa71a 100644
--- a/src/runtime.js
+++ b/src/runtime.js
@@ -375,6 +375,12 @@ function INSTANCE_OF(F) {
     return 1;
   }
 
+  // Check if function is bound, if so, get [[BoundFunction]] from it
+  // and use that instead of F.
+  var bindings = %BoundFunctionGetBindings(F);
+  if (bindings) {
+    F = bindings[kBoundFunctionIndex];  // Always a non-bound function.
+  }
   // Get the prototype of F; if it is not an object, throw an error.
   var O = F.prototype;
   if (!IS_SPEC_OBJECT(O)) {