[sensors](CrOS/Linux) Implement Sensor device manager for sensors

device/generic_sensor/platform_sensor_provider_base.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_base.h"
 
 #include <utility>
 
 #include "base/stl_util.h"
 #include "device/generic_sensor/public/interfaces/sensor_provider.mojom.h"
@@ skipping 14 matching lines @@
 void PlatformSensorProviderBase::CreateSensor(
     mojom::SensorType type,
     const CreateSensorCallback& callback) {
   DCHECK(CalledOnValidThread());
 
   if (!CreateSharedBufferIfNeeded()) {
     callback.Run(nullptr);
     return;
   }
 
-  mojo::ScopedSharedBufferMapping mapping = shared_buffer_handle_->MapAtOffset(
-      kReadingBufferSize, SensorReadingSharedBuffer::GetOffset(type));
+  mojo::ScopedSharedBufferMapping mapping = MapSharedBufferForType(type);
   if (!mapping) {
     callback.Run(nullptr);
     return;
   }
 
   auto it = requests_map_.find(type);
   if (it != requests_map_.end()) {
     it->second.push_back(callback);
   } else {  // This is the first CreateSensor call.
-    memset(mapping.get(), 0, kReadingBufferSize);
-
     requests_map_[type] = CallbackQueue({callback});
 
     CreateSensorInternal(
         type, std::move(mapping),
         base::Bind(&PlatformSensorProviderBase::NotifySensorCreated,
                    base::Unretained(this), type));
   }
 }
 
 scoped_refptr<PlatformSensor> PlatformSensorProviderBase::GetSensor(
@@ skipping 52 matching lines @@
 
   // Inform subscribers about the sensor.
   // |sensor| can be nullptr here.
   auto it = requests_map_.find(type);
   for (auto& callback : it->second)
     callback.Run(sensor);
 
   requests_map_.erase(type);
 }
 
+std::vector<mojom::SensorType>
+PlatformSensorProviderBase::GetPendingRequestTypes() {
+  std::vector<mojom::SensorType> request_types;
+  for (auto const& entry : requests_map_)
+    request_types.push_back(entry.first);
+  return request_types;
+}
+
+mojo::ScopedSharedBufferMapping
+PlatformSensorProviderBase::MapSharedBufferForType(mojom::SensorType type) {
+  mojo::ScopedSharedBufferMapping mapping = shared_buffer_handle_->MapAtOffset(
+      kReadingBufferSize, SensorReadingSharedBuffer::GetOffset(type));
+  memset(mapping.get(), 0, kReadingBufferSize);
+  return mapping;
+}
+
 }  // namespace device