accelerometer: Use base::NoDestructor for AccelerometerReader

This commit replaces base::Singleton with base::NoDestructor. It helps
to determine the lifetime of AccelerometerReader and avoid usages of it
on invalid threads.

BUG=b:171446270
TEST=run on nightfury(with iioservice) and helios(without iioservice)

Change-Id: I55686e712a381c860054db14a1df00346b16ce6a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2543171Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Cheng-Hao Yang <chenghaoyang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#828553}

ash/accelerometer/accelerometer_reader.cc

@@ -8,7 +8,7 @@
 
 #include "ash/accelerometer/accelerometer_file_reader.h"
 #include "ash/accelerometer/accelerometer_provider_mojo.h"
-#include "base/memory/singleton.h"
+#include "base/no_destructor.h"
 #include "base/posix/eintr_wrapper.h"
 #include "base/sequenced_task_runner.h"
 #include "base/threading/sequenced_task_runner_handle.h"
@@ -24,7 +24,8 @@ constexpr char kIioServiceGroupName[] = "iioservice";
 
 // static
 AccelerometerReader* AccelerometerReader::GetInstance() {
-  return base::Singleton<AccelerometerReader>::get();
+  static base::NoDestructor<AccelerometerReader> accelerometer_reader;
+  return accelerometer_reader.get();
 }
 
 void AccelerometerReader::Initialize() {

ash/accelerometer/accelerometer_reader.h

@@ -12,7 +12,7 @@
 
 namespace base {
 template <typename T>
-struct DefaultSingletonTraits;
+class NoDestructor;
 
 class SequencedTaskRunner;
 }  // namespace base
@@ -69,7 +69,7 @@ class ASH_EXPORT AccelerometerReader {
   virtual ~AccelerometerReader();
 
  private:
-  friend struct base::DefaultSingletonTraits<AccelerometerReader>;
+  friend class base::NoDestructor<AccelerometerReader>;
 
   // Worker that will run on the base::SequencedTaskRunner provided to
   // Initialize. It will determine accelerometer configuration, read the data,