Support "shared" histograms between processes.

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.
 
 # HOW TO WRITE CONDITIONALS IN THIS FILE
 # ======================================
 #
 # In many other places, one would write a conditional that expresses all the
 # cases when a source file is used or unused, and then either add or subtract
 # it from the sources list in that case
@@ skipping 480 matching lines @@
     "metrics/field_trial.cc",
     "metrics/field_trial.h",
     "metrics/histogram.cc",
     "metrics/histogram.h",
     "metrics/histogram_base.cc",
     "metrics/histogram_base.h",
     "metrics/histogram_delta_serialization.cc",
     "metrics/histogram_delta_serialization.h",
     "metrics/histogram_flattener.h",
     "metrics/histogram_macros.h",
+    "metrics/histogram_persistence.cc",
+    "metrics/histogram_persistence.h",
     "metrics/histogram_samples.cc",
     "metrics/histogram_samples.h",
     "metrics/histogram_snapshot_manager.cc",
     "metrics/histogram_snapshot_manager.h",
     "metrics/metrics_hashes.cc",
     "metrics/metrics_hashes.h",
     "metrics/persistent_memory_allocator.cc",
     "metrics/persistent_memory_allocator.h",
     "metrics/sample_map.cc",
     "metrics/sample_map.h",
@@ skipping 1634 matching lines @@
 
   # GYP: //base.gyp:base_java_unittest_support
   android_library("base_java_unittest_support") {
     deps = [
       ":base_java",
     ]
     java_files =
         [ "test/android/java/src/org/chromium/base/ContentUriTestUtils.java" ]
   }
 }