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

string_piece.h was moved into base/strings/ in r191206 -
https://chromiumcodereview.appspot.com/12982018/

TBR=brettw@chromium.org

Review URL: https://codereview.chromium.org/13374002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@191508 0039d316-1c4b-4281-b951-d872f2087c98


CrOS-Libchrome-Original-Commit: eb62f726194d68406047f2716e8ef500bf456d67
diff --git a/base/files/file_path.h b/base/files/file_path.h
index 2e0009d..cf3dc62 100644
--- a/base/files/file_path.h
+++ b/base/files/file_path.h
@@ -110,7 +110,7 @@
 #include "base/compiler_specific.h"
 #include "base/hash_tables.h"
 #include "base/string16.h"
-#include "base/string_piece.h"  // For implicit conversions.
+#include "base/strings/string_piece.h"  // For implicit conversions.
 #include "build/build_config.h"
 
 // Windows-style drive letter support and pathname separator characters can be