Remove unneeded includes of base/string_piece.h

chrome/test/v8_unit_test.h

 // Copyright (c) 2009 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.
 
 #ifndef CHROME_TEST_V8_UNIT_TEST_H_
 #define CHROME_TEST_V8_UNIT_TEST_H_
 
 #include <string>
 
-#include "base/string_piece.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "v8/include/v8.h"
 
+class StringPiece;
+
 // A superclass for unit tests that involve running JavaScript.  This class
 // sets up V8 context and has methods that make it easy to execute scripts in
 // this context as well as call functions in the context.
 class V8UnitTest : public testing::Test {
  public:
   V8UnitTest() {}
   virtual void SetUp();
 
  protected:
   // Executes the given script source in the context.  The specified script
@@ skipping 16 matching lines @@
   static v8::Handle<v8::Value> Log(const v8::Arguments& args);
 
   // Handle scope that is used throughout the life of this class.
   v8::HandleScope handle_scope_;
 
   // Context for the JavaScript in the test.
   v8::Handle<v8::Context> context_;
 };
 
 #endif  // CHROME_TEST_V8_UNIT_TEST_H_