Allow passing mock FrameLoaderClient to DummyPageHolder.

Source/core/editing/SurroundingTextTest.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/SurroundingText.h"
 
+#include "core/dom/Document.h"
 #include "core/dom/Position.h"
 #include "core/dom/Range.h"
 #include "core/dom/Text.h"
 #include "core/editing/VisibleSelection.h"
 #include "core/html/HTMLElement.h"
 #include "core/testing/DummyPageHolder.h"
 #include <gtest/gtest.h>
 
 using namespace blink;
 
@@ skipping 237 matching lines @@
         VisibleSelection selection = select(0, 7);
         SurroundingText surroundingText(*selection.firstRange(), 1337);
 
         EXPECT_EQ("This is outside of foo bar the selected node", surroundingText.content().simplifyWhiteSpace());
         EXPECT_EQ(20u, surroundingText.startOffsetInContent());
         EXPECT_EQ(27u, surroundingText.endOffsetInContent());
     }
 }
 
 } // anonymous namespace