accelerometer: Refactor AccelerometerProviderMojo

This commit simplifies the logic of AccelerometerProviderMojo by
limiting the usages on the UI thread.

BUG=b:175355860
TEST=unit tests and run on kohaku(hatch)

Change-Id: Ic43439a70b544848dcd3a948f996f81a9032687d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2586172Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Cheng-Hao Yang <chenghaoyang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#839061}

ash/accelerometer/accelerometer_provider_mojo.cc

@@ -30,12 +30,10 @@ constexpr base::TimeDelta kDelayReconnect =
 }  // namespace
 
 AccelerometerProviderMojo::AccelerometerProviderMojo()
-    : sensor_hal_client_(this),
-      observers_(
-          new base::ObserverListThreadSafe<AccelerometerReader::Observer>()),
-      update_(new AccelerometerUpdate()) {}
+    : update_(new AccelerometerUpdate()) {}
 
 void AccelerometerProviderMojo::PrepareAndInitialize() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   // This function should only be called once.
   DCHECK(!task_runner_);
 
@@ -49,40 +47,50 @@ void AccelerometerProviderMojo::PrepareAndInitialize() {
 
 void AccelerometerProviderMojo::AddObserver(
     AccelerometerReader::Observer* observer) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK(task_runner_);
 
-  // Do not move this into AddObserverOnThread, as the current task runner will
-  // be used in ObserverListThreadSafe::Notify.
-  observers_->AddObserver(observer);
+  observers_.AddObserver(observer);
 
-  task_runner_->PostNonNestableTask(
-      FROM_HERE, base::BindOnce(&AccelerometerProviderMojo::AddObserverOnThread,
-                                base::Unretained(this), observer));
+  one_time_read_ = true;
+
+  if (accelerometer_read_on_)
+    return;
+
+  for (auto& accelerometer : accelerometers_) {
+    if (!accelerometer.second.samples_observer.get())
+      continue;
+
+    accelerometer.second.samples_observer->SetEnabled(true);
+  }
 }
 
 void AccelerometerProviderMojo::RemoveObserver(
     AccelerometerReader::Observer* observer) {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK(task_runner_);
 
-  observers_->RemoveObserver(observer);
+  observers_.RemoveObserver(observer);
 }
 
 void AccelerometerProviderMojo::StartListenToTabletModeController() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   Shell::Get()->tablet_mode_controller()->AddObserver(this);
 }
 
 void AccelerometerProviderMojo::StopListenToTabletModeController() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   Shell::Get()->tablet_mode_controller()->RemoveObserver(this);
 }
 
 void AccelerometerProviderMojo::SetEmitEvents(bool emit_events) {
-  task_runner_->PostNonNestableTask(
-      FROM_HERE,
-      base::BindOnce(&AccelerometerProviderMojo::SetEmitEventsOnThread, this,
-                     emit_events));
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+  emit_events_ = emit_events;
 }
 
 void AccelerometerProviderMojo::OnTabletPhysicalStateChanged() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
+
   // Wait until the existence of the driver is determined.
   if (ec_lid_angle_driver_status_ == ECLidAngleDriverStatus::UNKNOWN) {
     pending_on_tablet_physical_state_changed_ = true;
@@ -514,9 +522,9 @@ void AccelerometerProviderMojo::OnSampleUpdatedCallback(
     return;
   }
 
-  observers_->Notify(FROM_HERE,
-                     &AccelerometerReader::Observer::OnAccelerometerUpdated,
-                     update_);
+  for (auto& observer : observers_)
+    observer.OnAccelerometerUpdated(update_);
+
   update_ = new AccelerometerUpdate();
 
   one_time_read_ = false;
@@ -532,12 +540,8 @@ void AccelerometerProviderMojo::OnSampleUpdatedCallback(
   }
 }
 
-void AccelerometerProviderMojo::SetEmitEventsOnThread(bool emit_events) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
-  emit_events_ = emit_events;
-}
-
 void AccelerometerProviderMojo::FailedToInitialize() {
+  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
   DCHECK_NE(initialization_state_, State::SUCCESS);
 
   LOG(ERROR) << "Failed to initialize for accelerometer read.";
@@ -548,21 +552,4 @@ void AccelerometerProviderMojo::FailedToInitialize() {
   sensor_hal_client_.reset();
 }
 
-void AccelerometerProviderMojo::AddObserverOnThread(
-    AccelerometerReader::Observer* observer) {
-  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
-
-  one_time_read_ = true;
-
-  if (accelerometer_read_on_)
-    return;
-
-  for (auto& accelerometer : accelerometers_) {
-    if (!accelerometer.second.samples_observer.get())
-      continue;
-
-    accelerometer.second.samples_observer->SetEnabled(true);
-  }
-}
-
 }  // namespace ash

ash/accelerometer/accelerometer_provider_mojo.h

@@ -17,7 +17,7 @@
 #include "ash/ash_export.h"
 #include "ash/public/cpp/tablet_mode_observer.h"
 #include "base/memory/ref_counted.h"
-#include "base/observer_list_threadsafe.h"
+#include "base/observer_list.h"
 #include "base/optional.h"
 #include "base/sequence_checker.h"
 #include "base/sequenced_task_runner.h"
@@ -121,18 +121,15 @@ class ASH_EXPORT AccelerometerProviderMojo
   // Called by |observers_|, containing a sample of the accelerometer.
   void OnSampleUpdatedCallback(int iio_device_id, std::vector<float> sample);
 
-  void SetEmitEventsOnThread(bool emit_events);
-
   // Sets FAILED to |initialization_state_| due to an error.
   void FailedToInitialize();
 
-  void AddObserverOnThread(AccelerometerReader::Observer* observer);
-
   // The task runner to use for blocking tasks.
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
 
   // The Mojo channel connecting to Sensor Hal Dispatcher.
-  mojo::Receiver<chromeos::sensors::mojom::SensorHalClient> sensor_hal_client_;
+  mojo::Receiver<chromeos::sensors::mojom::SensorHalClient> sensor_hal_client_{
+      this};
 
   // The Mojo channel to query and request for devices.
   mojo::Remote<chromeos::sensors::mojom::SensorService> sensor_service_remote_;
@@ -152,7 +149,7 @@ class ASH_EXPORT AccelerometerProviderMojo
   // |ec_lid_angle_driver_status_| is set.
   bool pending_on_tablet_physical_state_changed_ = false;
 
-  // One time read upon |AddObserverOnThread|.
+  // One time read upon |AddObserver|.
   // Some observers need to know ECLidAngleDriverStatus, and it's guaranteed to
   // be set before reading samples. When adding an observer, trigger at least
   // one sample to notify observers that ECLidAngleDriverStatus has been set.
@@ -164,8 +161,7 @@ class ASH_EXPORT AccelerometerProviderMojo
   bool emit_events_ = true;
 
   // The observers to notify of accelerometer updates.
-  scoped_refptr<base::ObserverListThreadSafe<AccelerometerReader::Observer>>
-      observers_;
+  base::ObserverList<AccelerometerReader::Observer>::Unchecked observers_;
 
   // The last seen accelerometer data.
   scoped_refptr<AccelerometerUpdate> update_;