Update AccelerometerReader to support separate iio devices

ash/content/display/screen_orientation_controller_chromeos_unittest.cc

 // 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.
 
 #include <vector>
 
 #include "ash/ash_switches.h"
 #include "ash/content/display/screen_orientation_controller_chromeos.h"
 #include "ash/display/display_info.h"
 #include "ash/display/display_manager.h"
@@ skipping 18 matching lines @@
 #include "ui/views/test/webview_test_helper.h"
 #include "ui/views/view.h"
 #include "ui/views/views_delegate.h"
 #include "ui/wm/public/activation_client.h"
 
 namespace ash {
 
 namespace {
 
 const float kDegreesToRadians = 3.1415926f / 180.0f;
-const float kMeanGravity = 9.8066f;
+const float kMeanGravity = -9.8066f;
 
 DisplayInfo CreateDisplayInfo(int64 id, const gfx::Rect& bounds) {
   DisplayInfo info(id, "dummy", false);
   info.SetBounds(bounds);
   return info;
 }
 
 void EnableMaximizeMode(bool enable) {
   Shell::GetInstance()
       ->maximize_mode_controller()
@@ skipping 598 matching lines @@
                               .GetActiveRotation());
 
   delegate()->SetDisplayRotation(kNewRotation,
                                  gfx::Display::ROTATION_SOURCE_ACTIVE);
 
   EXPECT_EQ(kNewRotation, display_manager->GetDisplayInfo(kInternalDisplayId)
                               .GetActiveRotation());
 }
 
 }  // namespace ash