generic_sensor: Fix PlatformSensorChromeOS StopSensor

Fixes <1aefce02> (generic_sensor: Add
PlatformSensor(Provider)ChromeOS)
Keeps |sensor_device_remote_| when stopping the reads, so that we can
resume the reads with StartSensor later.

BUG=b:172414302
TEST=run on nightfury(hatch)

Change-Id: I37057036ce9697fffad3e37eba6bca7654db398e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2546390
Commit-Queue: Cheng-Hao Yang <chenghaoyang@chromium.org>
Reviewed-by: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Cr-Commit-Position: refs/heads/master@{#835122}

services/device/generic_sensor/platform_sensor_chromeos.cc

@@ -203,7 +203,6 @@ bool PlatformSensorChromeOS::StartSensor(
 void PlatformSensorChromeOS::StopSensor() {
   DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
 
-  sensor_device_remote_.reset();
   receiver_.reset();
 }
 

services/device/generic_sensor/platform_sensor_chromeos_unittest.cc

@@ -179,13 +179,16 @@ TEST_P(PlatformSensorChromeOSOneChannelTest, GetSamples) {
 
   auto client = std::make_unique<testing::NiceMock<MockPlatformSensorClient>>();
   sensor_->AddClient(client.get());
-  sensor_->StartListening(client.get(),
-                          PlatformSensorConfiguration(
-                              GetSensorMaxAllowedFrequency(GetParam().first)));
+  double frequency = GetSensorMaxAllowedFrequency(GetParam().first);
+  sensor_->StartListening(client.get(), PlatformSensorConfiguration(frequency));
   EXPECT_TRUE(sensor_->IsActiveForTesting());
 
   WaitForAndCheckReading(client.get());
 
+  sensor_->StopListening(client.get(), PlatformSensorConfiguration(frequency));
+  sensor_->StartListening(client.get(), PlatformSensorConfiguration(frequency));
+  WaitForAndCheckReading(client.get());
+
   sensor_device_->ResetObserverRemote(receiver_id_);
 
   WaitForAndCheckReading(client.get());
@@ -328,13 +331,16 @@ TEST_P(PlatformSensorChromeOSAxesTest, GetSamples) {
 
   auto client = std::make_unique<testing::NiceMock<MockPlatformSensorClient>>();
   sensor_->AddClient(client.get());
-  sensor_->StartListening(client.get(),
-                          PlatformSensorConfiguration(
-                              GetSensorMaxAllowedFrequency(GetParam().first)));
+  double frequency = GetSensorMaxAllowedFrequency(GetParam().first);
+  sensor_->StartListening(client.get(), PlatformSensorConfiguration(frequency));
   EXPECT_TRUE(sensor_->IsActiveForTesting());
 
   WaitForAndCheckReading(client.get());
 
+  sensor_->StopListening(client.get(), PlatformSensorConfiguration(frequency));
+  sensor_->StartListening(client.get(), PlatformSensorConfiguration(frequency));
+  WaitForAndCheckReading(client.get());
+
   sensor_device_->ResetObserverRemote(receiver_id_);
 
   WaitForAndCheckReading(client.get());