Move Stats, histograms, and field trial into a metrics subdirectory of base and
put them in the base namespace.

TEST=it compiles
BUG=none

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@62510 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/base/base.gypi b/base/base.gypi
index bd15b00c..9329ccb 100644
--- a/base/base.gypi
+++ b/base/base.gypi
@@ -95,8 +95,6 @@
           'gtk_util.cc',
           'gtk_util.h',
           'hash_tables.h',
-          'histogram.cc',
-          'histogram.h',
           'iat_patch.cc',
           'iat_patch.h',
           'id_map.h',
@@ -138,6 +136,12 @@
           'message_pump_default.h',
           'message_pump_win.cc',
           'message_pump_win.h',
+          'metrics/histogram.cc',
+          'metrics/histogram.h',
+          'metrics/stats_counters.cc',
+          'metrics/stats_counters.h',
+          'metrics/stats_table.cc',
+          'metrics/stats_table.h',
           'mime_util.h',
           'mime_util_xdg.cc',
           'move.h',
@@ -223,10 +227,6 @@
           'singleton.h',
           'spin_wait.h',
           'stack_container.h',
-          'stats_counters.cc',
-          'stats_counters.h',
-          'stats_table.cc',
-          'stats_table.h',
           'stl_util-inl.h',
           'string_number_conversions.cc',
           'string_number_conversions.h',
@@ -429,8 +429,6 @@
           'event_recorder.cc',
           'event_recorder.h',
           'event_recorder_stubs.cc',
-          'field_trial.cc',
-          'field_trial.h',
           'file_descriptor_shuffle.cc',
           'file_descriptor_shuffle.h',
           'hmac.h',
@@ -449,6 +447,8 @@
           'message_pump_libevent.h',
           'message_pump_mac.h',
           'message_pump_mac.mm',
+          'metrics/field_trial.cc',
+          'metrics/field_trial.h',
           'nsimage_cache_mac.h',
           'nsimage_cache_mac.mm',
           'nss_util.cc',