Update the remaining include paths of base/string_piece.h to its new location.

chrome_frame/test/test_scrubber.h

 // Copyright (c) 2012 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.
 
 // The test scrubber cleans up machine state between tests.  This includes
 // killing all Internet Explorer processes, killing all Chrome processes spawned
 // by Chrome Frame, and deleting the user data directory.  The scrubber must be
 // installed before tests are run via |InstallTestScrubber|.
 //
 // Tests that lead to Chrome using a user data directory other than that used by
 // Chrome Frame in IE must provide that directory to the scrubber via
 // |OverrideDataDirectoryForThisTest()|.  Failure to do so will lead to the
 // scrubber failing to delete that directory.
 
 #ifndef CHROME_FRAME_TEST_TEST_SCRUBBER_H_
 #define CHROME_FRAME_TEST_TEST_SCRUBBER_H_
 
-#include "base/string_piece.h"
+#include "base/strings/string_piece.h"
 
 namespace testing {
 class UnitTest;
 }
 
 namespace chrome_frame_test {
 
 // Install the scrubber in |unit_test| (call before RUN_ALL_TESTS).
 void InstallTestScrubber(testing::UnitTest* unit_test);
 
 // Override the user data directory that will be deleted by the scrubber at the
 // completion of the current test.
 void OverrideDataDirectoryForThisTest(const base::StringPiece16& user_data_dir);
 
 }  // namespace chrome_frame_test
 
 #endif  // CHROME_FRAME_TEST_TEST_SCRUBBER_H_