Move base GN subprojects into base.

base/metrics/BUILD.gn

Index: base/metrics/BUILD.gn
diff --git a/base/metrics/BUILD.gn b/base/metrics/BUILD.gn
deleted file mode 100644
index 6dd212f887eb9b5541298123c844d1447ac84501..0000000000000000000000000000000000000000
--- a/base/metrics/BUILD.gn
+++ /dev/null
@@ -1,53 +0,0 @@
-# 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("metrics") {
-  sources = [
-    "bucket_ranges.cc",
-    "bucket_ranges.h",
-    "field_trial.cc",
-    "field_trial.h",
-    "histogram.cc",
-    "histogram.h",
-    "histogram_base.cc",
-    "histogram_base.h",
-    "histogram_delta_serialization.cc",
-    "histogram_delta_serialization.h",
-    "histogram_flattener.h",
-    "histogram_macros.h",
-    "histogram_samples.cc",
-    "histogram_samples.h",
-    "histogram_snapshot_manager.cc",
-    "histogram_snapshot_manager.h",
-    "metrics_hashes.cc",
-    "metrics_hashes.h",
-    "sample_map.cc",
-    "sample_map.h",
-    "sample_vector.cc",
-    "sample_vector.h",
-    "sparse_histogram.cc",
-    "sparse_histogram.h",
-    "statistics_recorder.cc",
-    "statistics_recorder.h",
-    "user_metrics.cc",
-    "user_metrics.h",
-    "user_metrics_action.h",
-  ]
-
-  configs += [ "//base:base_implementation" ]
-
-  deps = [
-    "//base/debug",
-    "//base/json",
-    "//base/memory",
-    "//base/process",
-  ]
-
-  allow_circular_includes_from = [
-    "//base/memory",
-    "//base/process",
-  ]
-
-  visibility = [ "//base/*" ]
-}