Remove NaCl.Startups histogram, this data is tracked in the NaCl plugin now

base/metrics/nacl_histogram.cc

-// Copyright (c) 2010 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.
-
-// nacl_histogram provides an enum and defines a macro that uses definitions
-// from histogram.h. Note that a histogram is an object that aggregates
-// statistics, and can summarize them in various forms, including ASCII
-// graphical, HTML, and numerically.
-// nacl_histogram information is used to compare how many times a native
-// client module has been loaded, compared to the number of chrome starts
-// and number of new tabs created.
-
-
-#include "base/metrics/histogram.h"
-#include "base/metrics/nacl_histogram.h"
-
-// To log histogram data about NaCl.Startups, call this function with
-// a NaClHistogramValue passed in as |hvalue|
-void UmaNaclHistogramEnumeration(NaClHistogramValue histogram_value) {
-  UMA_HISTOGRAM_ENUMERATION("NaCl.Startups", histogram_value,
-    NACL_MAX_HISTOGRAM);
-}
-