Fix AccelerometerFileReader to keep reading when auto-rotation is on

Auto rotation depends on the tablet physical state of the device,
not the UI state. Therefore AccelerometerFileReader should keep
reading accelerometer data as long as the device is physically
a tablet (detached or flipped).

BUG=1056862
TEST=Manually on hatch.

Change-Id: I96f6c8f1430fa2d50b20aaa97bd25e072bce098f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2079618Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745284}

ash/accelerometer/accelerometer_reader.cc

@@ -189,10 +189,7 @@ class AccelerometerFileReader
   void StopListenToTabletModeController();
 
   // TabletModeObserver:
-  // OnTabletModeStarted() triggers accelerometer read.
-  // OnTabletModeEnding() disables accelerometer read.
-  void OnTabletModeStarted() override;
-  void OnTabletModeEnding() override;
+  void OnTabletPhysicalStateChanged() override;
 
  private:
   friend class base::RefCountedThreadSafe<AccelerometerFileReader>;
@@ -544,31 +541,30 @@ void AccelerometerFileReader::StopListenToTabletModeController() {
   Shell::Get()->tablet_mode_controller()->RemoveObserver(this);
 }
 
-void AccelerometerFileReader::OnTabletModeStarted() {
+void AccelerometerFileReader::OnTabletPhysicalStateChanged() {
   // When CrOS EC lid angle driver is not present, accelerometer read is always
   // ON and can't be tuned. Thus AccelerometerFileReader no longer listens to
   // tablet mode event.
+  auto* tablet_mode_controller = Shell::Get()->tablet_mode_controller();
   if (ec_lid_angle_driver_ == NOT_SUPPORTED) {
-    Shell::Get()->tablet_mode_controller()->RemoveObserver(this);
+    tablet_mode_controller->RemoveObserver(this);
     return;
   }
 
-  task_runner_->PostNonNestableTask(
-      FROM_HERE, base::BindOnce(&AccelerometerFileReader::TriggerRead, this));
-}
-
-void AccelerometerFileReader::OnTabletModeEnding() {
-  if (ec_lid_angle_driver_ == NOT_SUPPORTED) {
-    Shell::Get()->tablet_mode_controller()->RemoveObserver(this);
-    return;
-  }
+  // Auto rotation is turned on when the device is physically used as a tablet
+  // (i.e. flipped or detached), regardless of the UI state (i.e. whether tablet
+  // mode is turned on or off).
+  const bool is_auto_rotation_on =
+      tablet_mode_controller->is_in_tablet_physical_state();
 
   task_runner_->PostNonNestableTask(
       FROM_HERE,
-      base::BindOnce(&AccelerometerFileReader::CancelRead, this));
+      is_auto_rotation_on
+          ? base::BindOnce(&AccelerometerFileReader::TriggerRead, this)
+          : base::BindOnce(&AccelerometerFileReader::CancelRead, this));
 }
 
-AccelerometerFileReader::~AccelerometerFileReader() {}
+AccelerometerFileReader::~AccelerometerFileReader() = default;
 
 bool AccelerometerFileReader::InitializeAccelerometer(
     const base::FilePath& iio_path,