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

base/field_trial_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 FieldTrial class
 
 #include "base/field_trial.h"
 
-#include "base/logging.h"
 #include "base/string_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 class FieldTrialTest : public testing::Test {
  public:
   FieldTrialTest() : trial_list_() { }
 
  private:
   FieldTrialList trial_list_;
 };
@@ skipping 88 matching lines @@
       EXPECT_EQ(winner_index, -2);
       winner_index = might_win;
       StringAppendF(&winner_name, "_%d", might_win);
       EXPECT_EQ(winner_name, trial->group_name());
     }
   }
   EXPECT_GE(winner_index, 0);
   EXPECT_EQ(trial->group(), winner_index);
   EXPECT_EQ(winner_name, trial->group_name());
 }