Update to Chromium //base at Chromium commit e3a753f17bac62738b0dbf0b36510f767b081e4b.

memory/BUILD.gn

 # Copyright (c) 2015 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.
 
 source_set("memory") {
   sources = [
     "aligned_memory.cc",
     "aligned_memory.h",
     "discardable_memory.cc",
     "discardable_memory.h",
@@ skipping 51 matching lines @@
       "shared_memory_posix.cc",
     ]
   } else {
     sources -= [ "shared_memory_nacl.cc" ]
   }
 
   if (is_mac) {
     sources -= [ "shared_memory_posix.cc" ]
   }
 
+  if (is_ios) {
+    set_sources_assignment_filter([])
+    sources += [
+      "shared_memory_handle_mac.cc",
+      "shared_memory_mac.cc",
+    ]
+    set_sources_assignment_filter(sources_assignment_filter)
+  }
+
   if (is_android) {
     deps = [
       "//third_party/ashmem",
     ]
   }
 
   configs += [ "//base:base_implementation" ]
 
   visibility = [ "//base/*" ]
 }