[bindings] Migrate V8TestingScope out of V8Binding.h/cpp

Source/bindings/core/v8/V8BindingTest.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.
 
 #include "config.h"
 #include "bindings/core/v8/V8Binding.h"
 
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/ToV8.h"
+#include "bindings/core/v8/V8TestingScope.h"
 #include "wtf/Vector.h"
 #include <gtest/gtest.h>
 
 namespace blink {
 
 namespace {
 
 class V8BindingTest : public ::testing::Test {
 public:
     V8BindingTest() : m_scope(v8::Isolate::GetCurrent()) { }
@@ skipping 87 matching lines @@
         EXPECT_EQ(3U, stringVectorVector[1].size());
         EXPECT_EQ("x", stringVectorVector[1][0]);
         EXPECT_EQ("y", stringVectorVector[1][1]);
         EXPECT_EQ("z", stringVectorVector[1][2]);
     }
 }
 
 } // namespace
 
 } // namespace blink