Update from https://crrev.com/327068

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",
     "discardable_memory_allocator.cc",
     "discardable_memory_allocator.h",
     "discardable_shared_memory.cc",
     "discardable_shared_memory.h",
     "linked_ptr.h",
     "manual_constructor.h",
     "memory_pressure_listener.cc",
     "memory_pressure_listener.h",
+    "memory_pressure_monitor.cc",
+    "memory_pressure_monitor.h",
     "raw_scoped_refptr_mismatch_checker.h",
     "ref_counted.cc",
     "ref_counted.h",
     "ref_counted_delete_on_message_loop.h",
     "ref_counted_memory.cc",
     "ref_counted_memory.h",
     "scoped_policy.h",
     "scoped_ptr.h",
     "scoped_vector.h",
     "shared_memory.h",
@@ skipping 18 matching lines @@
       "shared_memory_posix.cc",
     ]
   } else {
     sources -= [ "shared_memory_nacl.cc" ]
   }
 
   configs += [ "//base:base_implementation" ]
 
   visibility = [ "//base/*" ]
 }