[bindings] Support is_explicit_nullable for method arguments.

Source/bindings/tests/results/core/V8TestObject.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This file has been auto-generated by code_generator_v8.py. DO NOT MODIFY!
 
 #include "config.h"
 #include "V8TestObject.h"
 
 #include "bindings/core/v8/BindingSecurity.h"
@@ skipping 6197 matching lines @@
     TRACE_EVENT_SET_SAMPLING_STATE("v8", "V8Execution");
 }
 
 static void voidMethodNullableVoidCallbackFunctionArgMethod(const v8::FunctionCallbackInfo<v8::Value>& info)
 {
     if (UNLIKELY(info.Length() < 1)) {
         V8ThrowException::throwException(createMinimumArityTypeErrorForMethod(info.GetIsolate(), "voidMethodNullableVoidCallbackFunctionArg", "TestObject", 1, info.Length()), info.GetIsolate());
         return;
     }
     TestObject* impl = V8TestObject::toImpl(info.Holder());
-    ScriptValue voidCallbackFunctionArg;
+    Nullable<ScriptValue> voidCallbackFunctionArg;

[Jens Widell, 2015/03/02 07:53:13]

This is wrong; ScriptValue can store null, so shouldn't be "explicitly
nullable".

I guess idl_type.is_callback_function is the condition we need to add to
v8_types.cpp_type_has_null_value().

     {
         if (!info[0]->IsFunction() && !info[0]->IsNull()) {
             V8ThrowException::throwTypeError(info.GetIsolate(), ExceptionMessages::failedToExecute("voidMethodNullableVoidCallbackFunctionArg", "TestObject", "The callback provided as parameter 1 is not a function."));
             return;
         }
         voidCallbackFunctionArg = ScriptValue(ScriptState::current(info.GetIsolate()), info[0]);
     }
     impl->voidMethodNullableVoidCallbackFunctionArg(voidCallbackFunctionArg);
 }
 
@@ skipping 6453 matching lines @@
         return false;
 
     ScriptState::Scope scope(scriptState);
     v8::Local<v8::Value> holder = toV8(holderImpl, scriptState->context()->Global(), scriptState->isolate());
 
     ExceptionState exceptionState(ExceptionState::SetterContext, "enumForPrivateScript", "TestObject", scriptState->context()->Global(), scriptState->isolate());
     return PrivateScriptRunner::runDOMAttributeSetter(scriptState, scriptStateInUserScript, "TestObject", "enumForPrivateScript", holder, v8String(scriptState->isolate(), cppValue));
 }
 
 } // namespace blink