Update from chromium https://crrev.com/304586

base/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 381 matching lines @@
     "metrics/sample_vector.h",
     "metrics/bucket_ranges.cc",
     "metrics/bucket_ranges.h",
     "metrics/histogram.cc",
     "metrics/histogram.h",
     "metrics/histogram_base.cc",
     "metrics/histogram_base.h",
     "metrics/histogram_delta_serialization.cc",
     "metrics/histogram_delta_serialization.",
     "metrics/histogram_flattener.h",
+    "metrics/histogram_macros.h",
     "metrics/histogram_samples.cc",
     "metrics/histogram_samples.h",
     "metrics/histogram_snapshot_manager.cc",
     "metrics/histogram_snapshot_manager.h",
     "metrics/sparse_histogram.cc",
     "metrics/sparse_histogram.h",
     "metrics/statistics_recorder.cc",
     "metrics/statistics_recorder.h",
     "metrics/stats_counters.cc",
     "metrics/stats_counters.h",
@@ skipping 983 matching lines @@
   }
 
   if (is_android) {
     deps += [
       "//testing/android:native_test_native_code",
     ]
     set_sources_assignment_filter([])
     sources += [ "debug/proc_maps_linux_unittest.cc" ]
     set_sources_assignment_filter(sources_assignment_filter)
   }
+
+  if (is_win) {
+    # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+    cflags = [ "/wd4267" ]
+  }
 }
 
 if (is_android) {
   # GYP: //base.gyp:base_jni_headers
   generate_jni("base_jni_headers") {
     sources = [
       "android/java/src/org/chromium/base/ApplicationStatus.java",
       "android/java/src/org/chromium/base/BuildInfo.java",
       "android/java/src/org/chromium/base/CommandLine.java",
       "android/java/src/org/chromium/base/ContentUriUtils.java",
@@ skipping 90 matching lines @@
   # GYP: //base.gyp:base_unittests_apk
   unittest_apk("base_unittests_apk") {
     deps = [
       ":base_java",
       ":base_java_unittest_support",
       ":base_unittests",
     ]
     unittests_dep = ":base_unittests"
   }
 }