Build third-party code with -Wall, build chromium_code with -Wextra on Linux

chrome/browser/android/data_usage/tab_data_use_entry_unittest.cc

 // Copyright 2015 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.
 
 #include "chrome/browser/android/data_usage/tab_data_use_entry.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <string>
@@ skipping 55 matching lines @@
 
 class TabDataUseEntryTest : public testing::Test {
  public:
   TabDataUseEntryTest() {
     tab_model_.reset(new DataUseTabModel());
     tick_clock_ = new SimpleOffsetTestTickClock();
     tab_model_->tick_clock_.reset(tick_clock_);
     tab_entry_.reset(new TabDataUseEntry(tab_model_.get()));
   }
 
-  const size_t GetMaxSessionsPerTab() const {
+  size_t GetMaxSessionsPerTab() const {
     return tab_model_->max_sessions_per_tab();
   }
 
   const base::TimeDelta& GetClosedTabExpirationDuration() const {
     return tab_model_->closed_tab_expiration_duration();
   }
 
   const base::TimeDelta& GetOpenTabExpirationDuration() const {
     return tab_model_->open_tab_expiration_duration();
   }
@@ skipping 453 matching lines @@
   EXPECT_TRUE(tab_entry_->EndTracking());
 
   histogram_tester.ExpectUniqueSample(
       kUMAOldInactiveSessionRemovalDurationSecondsHistogram,
       base::TimeDelta::FromSeconds(30).InMilliseconds(), 1);
 }
 
 }  // namespace android
 
 }  // namespace chrome