Move part of metrics from chrome/common to components

components/metrics/proto/histogram_event.proto

 // Copyright (c) 2012 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.
 //
 // Histogram-collected metrics.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
 
@@ skipping 25 matching lines @@
     // This field was intended to provide extra redundancy to detect corrupted
     // records, but was never used.  As of M31, it is no longer sent by Chrome
     // clients to reduce the UMA upload size.
     optional int32 bucket_index = 3 [deprecated = true];
 
     // The number of entries in this bucket.
     optional int64 count = 4;
   }
   repeated Bucket bucket = 3;
 }