Update from https://crrev.com/308331

base/base.gypi

Index: base/base.gypi
diff --git a/base/base.gypi b/base/base.gypi
index f9451662c086f77c3be269eeab051684bb344579..5ec41425ad6dad545337a46ccc5ffb11e542ba58 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -122,6 +122,8 @@
           'callback_internal.h',
           'callback_list.h',
           'cancelable_callback.h',
+          'chromeos/memory_pressure_observer_chromeos.cc',
+          'chromeos/memory_pressure_observer_chromeos.h',
           'command_line.cc',
           'command_line.h',
           'compiler_specific.h',
@@ -251,6 +253,8 @@
           'ios/ios_util.mm',
           'ios/scoped_critical_action.h',
           'ios/scoped_critical_action.mm',
+          'ios/weak_nsobject.h',
+          'ios/weak_nsobject.mm',
           'json/json_file_value_serializer.cc',
           'json/json_file_value_serializer.h',
           'json/json_parser.cc',
@@ -979,6 +983,11 @@
           ['OS == "win" and >(nacl_untrusted_build)==1', {
               'sources/': [ ['exclude', '\\.h$'] ],
           }],
+          # Enable more direct string conversions on platforms with native utf8
+          # strings
+          ['OS=="mac" or OS=="ios" or <(chromeos)==1 or <(chromecast)==1', {
+            'defines': ['SYSTEM_NATIVE_UTF8'],
+          }],
         ],
       }],
       ['base_i18n_target==1', {