Better arity checks for overloads

Source/bindings/v8/custom/V8ElementCustom.cpp

 /*
  * Copyright (C) 2014 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 146 matching lines @@
     ASSERT(impl);
     RefPtr<AnimationPlayer> result = ElementAnimation::animate(*impl, keyframes, timingInput, exceptionState);
     if (exceptionState.throwIfNeeded())
         return;
     v8SetReturnValueFast(info, WTF::getPtr(result.release()), impl);
 }
 
 void V8Element::animateMethodCustom(const v8::FunctionCallbackInfo<v8::Value>& info)
 {
     v8::Isolate* isolate = info.GetIsolate();
+    ExceptionState exceptionState(ExceptionState::ExecutionContext, "animate", "Element", info.Holder(), isolate);
     // AnimationPlayer animate(
     //     (AnimationEffect or sequence<Dictionary>)? effect,
     //     optional (double or Dictionary) timing);
     switch (info.Length()) {
     case 1:
         // null resolved as to AnimationEffect, as if the member were nullable:
         // (AnimationEffect? or sequence<Dictionary>)
         // instead of the *union* being nullable:
         // (AnimationEffect or sequence<Dictionary>)?
         // AnimationPlayer animate(AnimationEffect? effect);
@@ skipping 45 matching lines @@
             return;
         }
         // [MeasureAs=ElementAnimateKeyframeListEffectDoubleTiming]
         // AnimationPlayer animate(sequence<Dictionary> effect, double timing);
         if (info[0]->IsArray()) {
             UseCounter::count(callingExecutionContext(isolate), UseCounter::ElementAnimateKeyframeListEffectDoubleTiming);
             animate5Method(info);
             return;
         }
         break;
-    }
-    ExceptionState exceptionState(ExceptionState::ExecutionContext, "animate", "Element", info.Holder(), isolate);
-    if (UNLIKELY(info.Length() < 1)) {
-        throwArityTypeError(exceptionState, 1, info.Length());
+    default:
+        throwArityTypeError(exceptionState, "[1]", info.Length());
         return;
+        break;
     }
     exceptionState.throwTypeError("No function was found that matched the signature provided.");
     exceptionState.throwIfNeeded();
 }
 
 } // namespace WebCore