Make `chrome` target build without unused data members on Linux.

chrome/browser/metrics/chrome_metrics_service_client.h

 // Copyright 2014 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.
 
 #ifndef CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_CLIENT_H_
 #define CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_CLIENT_H_
 
 #include <stdint.h>
 
 #include <string>
@@ skipping 131 matching lines @@
   base::ThreadChecker thread_checker_;
 
   // Weak pointer to the MetricsStateManager.
   metrics::MetricsStateManager* metrics_state_manager_;
 
   // The MetricsService that |this| is a client of.
   scoped_ptr<metrics::MetricsService> metrics_service_;
 
   content::NotificationRegistrar registrar_;
 
+#if defined(OS_CHROMEOS)
   // On ChromeOS, holds a weak pointer to the ChromeOSMetricsProvider instance
   // that has been registered with MetricsService. On other platforms, is NULL.
   ChromeOSMetricsProvider* chromeos_metrics_provider_;
+#endif
 
   // Saved callback received from CollectFinalMetricsForLog().
   base::Closure collect_final_metrics_done_callback_;
 
   // Indicates that collect final metrics step is running.
   bool waiting_for_collect_final_metrics_step_;
 
   // Number of async histogram fetch requests in progress.
   int num_async_histogram_fetches_in_progress_;
 
@@ skipping 39 matching lines @@
   // Whether this client has already uploaded profiler data during this session.
   // Profiler data is uploaded at most once per session.
   bool has_uploaded_profiler_data_;
 
   base::WeakPtrFactory<ChromeMetricsServiceClient> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeMetricsServiceClient);
 };
 
 #endif  // CHROME_BROWSER_METRICS_CHROME_METRICS_SERVICE_CLIENT_H_