Make ExtensionIconSet::ContainsPath use StringPiece.

chrome/test/BUILD.gn

 # 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.
 
 import("//build/config/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//chrome/common/features.gni")
@@ skipping 3990 matching lines @@
       "../browser/web_applications/web_app_mac_unittest.mm",
       "../browser/web_applications/web_app_unittest.cc",
       "../common/extensions/api/commands/commands_manifest_unittest.cc",
       "../common/extensions/api/common_extension_api_unittest.cc",
       "../common/extensions/api/extension_action/browser_action_manifest_unittest.cc",
       "../common/extensions/api/extension_action/page_action_manifest_unittest.cc",
       "../common/extensions/api/storage/storage_schema_manifest_handler_unittest.cc",
       "../common/extensions/chrome_extensions_client_unittest.cc",
       "../common/extensions/chrome_manifest_url_handlers_unittest.cc",
       "../common/extensions/command_unittest.cc",
-      "../common/extensions/extension_icon_set_unittest.cc",
       "../common/extensions/extension_unittest.cc",
       "../common/extensions/feature_switch_unittest.cc",
       "../common/extensions/manifest_handlers/automation_unittest.cc",
       "../common/extensions/manifest_handlers/content_scripts_manifest_unittest.cc",
       "../common/extensions/manifest_handlers/exclude_matches_manifest_unittest.cc",
       "../common/extensions/manifest_handlers/settings_overrides_handler_unittest.cc",
       "../common/extensions/manifest_handlers/ui_overrides_handler_unittest.cc",
       "../common/extensions/manifest_tests/chrome_manifest_test.cc",
       "../common/extensions/manifest_tests/chrome_manifest_test.h",
       "../common/extensions/manifest_tests/extension_manifests_about_unittest.cc",
@@ skipping 1062 matching lines @@
 }
 
 if (is_win) {
   loadable_module("conflicts_dll") {
     testonly = true
     sources = [
       "conflicts/conflicts_dll.cc",
     ]
   }
 }