Fix ODR violation that can break WTF::String pretty printing in tests.

Source/core/editing/FrameSelectionTest.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 "core/editing/FrameSelection.h"
 
 #include "bindings/core/v8/ExceptionStatePlaceholder.h"
 #include "core/dom/Document.h"
 #include "core/dom/Element.h"
 #include "core/dom/Text.h"
 #include "core/frame/FrameView.h"
 #include "core/html/HTMLBodyElement.h"
 #include "core/html/HTMLDocument.h"
 #include "core/testing/DummyPageHolder.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefPtr.h"
 #include "wtf/StdLibExtras.h"
-#include "wtf/testing/WTFTestHelpers.h"
 #include <gtest/gtest.h>
 
 namespace blink {
 
 class FrameSelectionTest : public ::testing::Test {
 protected:
     void SetUp() override;
 
     DummyPageHolder& dummyPageHolder() const { return *m_dummyPageHolder; }
     HTMLDocument& document() const;
@@ skipping 149 matching lines @@
     EXPECT_EQ_SELECTED_TEXT("Bar Baz");
     // "Fo<o B|ar Baz," with the Character granularity.
     selection().moveRangeSelection(VisiblePosition(Position(text, 5)), VisiblePosition(Position(text, 2)), CharacterGranularity);
     EXPECT_EQ_SELECTED_TEXT("o B");
     // "Fo<o B|ar Baz," with the Word granularity.
     selection().moveRangeSelection(VisiblePosition(Position(text, 5)), VisiblePosition(Position(text, 2)), WordGranularity);
     EXPECT_EQ_SELECTED_TEXT("Foo Bar");
 }
 
 } // namespace blink