[sensors] Introduce asynchronous way to create sensors.

device/generic_sensor/sensor_provider_impl.cc

Index: device/generic_sensor/sensor_provider_impl.cc
diff --git a/device/generic_sensor/sensor_provider_impl.cc b/device/generic_sensor/sensor_provider_impl.cc
index 2cdb1c5a32d5b32ac3c3b97070d0a3a2f0983d33..a27759d07302c412f43a5273747a4a0140664333 100644
--- a/device/generic_sensor/sensor_provider_impl.cc
+++ b/device/generic_sensor/sensor_provider_impl.cc
@@ -32,7 +32,7 @@ void SensorProviderImpl::Create(mojom::SensorProviderRequest request) {
 }
 
 SensorProviderImpl::SensorProviderImpl(PlatformSensorProvider* provider)
-    : provider_(provider) {
+    : provider_(provider), weak_ptr_factory_(this) {

[Mikhail, 2016/09/27 11:29:19]

nit: next line

[maksims (do not use this acc), 2016/09/27 12:22:08]

Should I really move to the next line? Git cl format makes it back like this.

   DCHECK(provider_);
 }
 
@@ -49,10 +49,24 @@ void SensorProviderImpl::GetSensor(mojom::SensorType type,
 
   scoped_refptr<PlatformSensor> sensor = provider_->GetSensor(type);
   if (!sensor) {
-    sensor = provider_->CreateSensor(
-        type, mojom::SensorInitParams::kReadBufferSize, GetBufferOffset(type));
+    CreateSensorCallback cb = base::Bind(
+        &SensorProviderImpl::CreateSensor, weak_ptr_factory_.GetWeakPtr(), type,
+        base::Passed(&cloned_handle), base::Passed(&sensor_request), callback);
+    provider_->CreateSensor(type, mojom::SensorInitParams::kReadBufferSize,
+                            GetBufferOffset(type), cb);
+    return;
   }
 
+  CreateSensor(type, std::move(cloned_handle), std::move(sensor_request),
+               callback, std::move(sensor));
+}
+
+void SensorProviderImpl::CreateSensor(

[Mikhail, 2016/09/27 11:29:19]

worth renaming to 'SensorCreated'. it does not create sensor actually.

[maksims (do not use this acc), 2016/09/27 12:19:37]

Done.

+    mojom::SensorType type,
+    mojo::ScopedSharedBufferHandle cloned_handle,
+    mojom::SensorRequest sensor_request,
+    const GetSensorCallback& callback,
+    scoped_refptr<PlatformSensor> sensor) {
   if (!sensor) {
     callback.Run(nullptr, nullptr);
     return;