patch from chinmaygarde@ to make progress on mac, ios.

base/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 29 matching lines @@
     "shared_memory_mac.cc",
     "shared_memory_nacl.cc",
     "shared_memory_posix.cc",
     "shared_memory_win.cc",
     "singleton.cc",
     "singleton.h",
     "weak_ptr.cc",
     "weak_ptr.h",
   ]
   if (is_ios) {
-    sources -= [ "shared_memory_posix.cc" ]
+    sources -= [
+      "discardable_shared_memory.cc",
+      "shared_memory_posix.cc",
+    ]
   }
 
   if (is_nacl) {
     sources -= [
       "discardable_memory.cc",
       "discardable_memory.h",
       "discardable_memory_allocator.cc",
       "discardable_memory_allocator.h",
       "discardable_shared_memory.cc",
       "discardable_shared_memory.h",
@@ skipping 10 matching lines @@
   if (is_android) {
     deps = [
       "//third_party/ashmem",
     ]
   }
 
   configs += [ "//base:base_implementation" ]
 
   visibility = [ "//base/*" ]
 }