Add uma stats to help evaluate the impact of changes to the quota allocation logic.

storage/common/BUILD.gn

 # Copyright 2014 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.
 
 component("common") {
   output_name = "storage_common"
   sources = [
     "blob_storage/blob_item_bytes_request.cc",
     "blob_storage/blob_item_bytes_request.h",
     "blob_storage/blob_item_bytes_response.cc",
@@ skipping 11 matching lines @@
     "fileapi/file_system_info.cc",
     "fileapi/file_system_info.h",
     "fileapi/file_system_mount_option.h",
     "fileapi/file_system_types.h",
     "fileapi/file_system_util.cc",
     "fileapi/file_system_util.h",
     "quota/quota_status_code.cc",
     "quota/quota_status_code.h",
     "quota/quota_types.h",
     "storage_common_export.h",
+    "storage_histograms.cc",
+    "storage_histograms.h",
   ]
 
   # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
   configs += [
     "//build/config/compiler:no_size_t_to_int_warning",
     "//build/config/compiler:wexit_time_destructors",
   ]
 
   defines = [ "STORAGE_COMMON_IMPLEMENTATION" ]
 
@@ skipping 16 matching lines @@
   ]
 
   deps = [
     ":common",
     "//base/test:run_all_unittests",
     "//base/test:test_support",
     "//testing/gtest",
     "//url",
   ]
 }