Fix virtual/override/final usage in Source/web/.

Source/web/PluginPlaceholderImplTest.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 "web/PluginPlaceholderImpl.h"
 
 #include "core/CSSPropertyNames.h"
 #include "core/CSSValueKeywords.h"
 #include "core/HTMLNames.h"
@@ skipping 13 matching lines @@
 using testing::Return;
 
 namespace blink {
 namespace {
 
 using HTMLNames::scriptTag;
 
 class MockWebPluginPlaceholder : public WebPluginPlaceholder {
 public:
     static PassOwnPtr<MockWebPluginPlaceholder> create() { return adoptPtr(new MockWebPluginPlaceholder); }
-    virtual ~MockWebPluginPlaceholder() { }
+    ~MockWebPluginPlaceholder() override { }
 
     MOCK_CONST_METHOD0(message, WebString());
     MOCK_CONST_METHOD0(isCloseable, bool());
 
 private:
     MockWebPluginPlaceholder()
     {
         ON_CALL(*this, message()).WillByDefault(Return(WebString()));
     }
 };
@@ skipping 74 matching lines @@
 {
     EXPECT_CALL(webPluginPlaceholder(), isCloseable()).WillOnce(Return(false));
     pluginPlaceholder().loadIntoContainer(documentFragment());
     RefPtrWillBeRawPtr<Element> closeButton = documentFragment().getElementById("plugin-placeholder-close-button");
     EXPECT_NE(nullptr, closeButton);
     EXPECT_TRUE(isHiddenWithInlineStyle(closeButton.get()));
 }
 
 } // namespace
 } // namespace blink