[sensors] Introduce asynchronous way to create sensors.

device/generic_sensor/platform_sensor_provider_android.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "device/generic_sensor/platform_sensor_provider.h"
 
 #include "base/android/context_utils.h"
 #include "base/android/scoped_java_ref.h"
 #include "base/memory/singleton.h"
 #include "device/generic_sensor/platform_sensor_android.h"
 #include "jni/PlatformSensorProvider_jni.h"
 
 using base::android::AttachCurrentThread;
 using base::android::ScopedJavaLocalRef;
 
 namespace device {
 
 class PlatformSensorProviderAndroid : public PlatformSensorProvider {
  public:
   PlatformSensorProviderAndroid();
   ~PlatformSensorProviderAndroid() override;
 
   static PlatformSensorProviderAndroid* GetInstance();
 
  protected:
-  scoped_refptr<PlatformSensor> CreateSensorInternal(
-      mojom::SensorType type,
-      mojo::ScopedSharedBufferMapping mapping,
-      uint64_t buffer_size) override;
+  void CreateSensorInternal(mojom::SensorType type,
+                            mojo::ScopedSharedBufferMapping mapping,
+                            uint64_t buffer_size,
+                            const CreateSensorCallback& callback) override;
 
  private:
   // Java object org.chromium.device.sensors.PlatformSensorProvider
   base::android::ScopedJavaGlobalRef<jobject> j_object_;
 
   DISALLOW_COPY_AND_ASSIGN(PlatformSensorProviderAndroid);
 };
 
 // static
 PlatformSensorProvider* PlatformSensorProvider::GetInstance() {
   return PlatformSensorProviderAndroid::GetInstance();
 }
 
 // static
 PlatformSensorProviderAndroid* PlatformSensorProviderAndroid::GetInstance() {
   return base::Singleton<
       PlatformSensorProviderAndroid,
       base::LeakySingletonTraits<PlatformSensorProviderAndroid>>::get();
 }
 
 PlatformSensorProviderAndroid::PlatformSensorProviderAndroid() {
   JNIEnv* env = AttachCurrentThread();
   j_object_.Reset(Java_PlatformSensorProvider_create(
       env, base::android::GetApplicationContext()));
 }
 
 PlatformSensorProviderAndroid::~PlatformSensorProviderAndroid() = default;
 
-scoped_refptr<PlatformSensor>
-PlatformSensorProviderAndroid::CreateSensorInternal(
+void PlatformSensorProviderAndroid::CreateSensorInternal(
     mojom::SensorType type,
     mojo::ScopedSharedBufferMapping mapping,
-    uint64_t buffer_size) {
+    uint64_t buffer_size,
+    const CreateSensorCallback& callback) {
   JNIEnv* env = AttachCurrentThread();
   ScopedJavaLocalRef<jobject> sensor = Java_PlatformSensorProvider_createSensor(
       env, j_object_.obj(), static_cast<jint>(type));
 
   if (!sensor.obj())
-    return nullptr;
+    callback.Run(nullptr);
 
-  return new PlatformSensorAndroid(type, std::move(mapping), buffer_size, this,
-                                   sensor);
+  scoped_refptr<PlatformSensorAndroid> concrete_sensor =
+      new PlatformSensorAndroid(type, std::move(mapping), buffer_size, this,
+                                sensor);
+  callback.Run(concrete_sensor);
 }
 
 }  // namespace device