Remove logging.h from cc files that don't use it.

base/histogram_unittest.cc

 // Copyright (c) 2006-2008 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.
 
 // Test of Histogram class
 
 #include "base/histogram.h"
-#include "base/logging.h"
 #include "base/string_util.h"
 #include "base/time.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using base::TimeDelta;
 
 namespace {
 
 class HistogramTest : public testing::Test {
 };
@@ skipping 266 matching lines @@
   AssetCountFunction(-100);  // Remove a sample from the bucket for 100.
   our_debug_histogram->SnapshotSample(&sample);  // Extract data set.
 
   // Verify that the bucket is now empty, as are all the other buckets.
   for (size_t i = 0; i < our_debug_histogram->bucket_count(); ++i) {
     EXPECT_EQ(0, sample.counts(i)) << "extra count in bucket " << i;
   }
 }
 
 }  // namespace