Fix SysStrings unit test failure on Chromecast

base/test/BUILD.gn

 # Copyright (c) 2013 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/ui.gni")
 
 if (is_android) {
   import("//build/config/android/rules.gni")
 }
 
@@ skipping 109 matching lines @@
     "//third_party/libxml",
     "//third_party/icu:icuuc",
   ]
 
   if (!is_posix) {
     sources -= [
       "scoped_locale.cc",
       "scoped_locale.h",
     ]
   }
+
+  # Allow more direct string conversions on platforms with native utf8
+  # strings
+  if (is_mac || is_ios || is_chromeos) {
+    defines += [ "SYSTEM_NATIVE_UTF8" ]
+  }
+
   if (is_ios) {
     # iOS uses its own unit test launcher.
     sources -= [ "launcher/unit_test_launcher.cc" ]
 
     # Pull in specific Mac files for iOS (which have been filtered out
     # by file name rules).
     set_sources_assignment_filter([])
     sources += [ "test_file_util_mac.cc" ]
   }
 
@@ skipping 31 matching lines @@
 }
 
 if (is_android) {
   generate_jni("base_unittests_jni_headers") {
     sources = [
       "android/java/src/org/chromium/base/ContentUriTestUtils.java",
     ]
     jni_package = "base"
   }
 }