[sensors] Introduce Generic Sensor API interfaces

device/sensors/sensor_provider_impl.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/sensors/sensor_provider_impl.h"
+
+#include <utility>
+
+#include "device/sensors/platform_sensor_provider.h"
+#include "device/sensors/sensor_impl.h"
+
+namespace device {
+namespace mojom {
+
+namespace {
+const uint64_t kSharedBufferSizeInBytes =
+    SensorReadBuffer::kReadBufferSize * static_cast<uint64_t>(SensorType::LAST);
+}
+
+PlatformSensorProvider* SensorProviderImpl::s_provider_ = nullptr;
+
+// static
+void SensorProviderImpl::Create(
+    mojo::InterfaceRequest<SensorProvider> request) {
+  if (!s_provider_)
+    s_provider_ = PlatformSensorProvider::Create(kSharedBufferSizeInBytes);
+
+  if (s_provider_) {

[Reilly Grant (use Gerrit), 2016/07/27 22:07:58]

nit: No braces for single-line if.

[Mikhail, 2016/08/09 19:38:28]

Done.

+    new SensorProviderImpl(std::move(request));
+  }
+}
+
+SensorProviderImpl::SensorProviderImpl(
+    mojo::InterfaceRequest<SensorProvider> request)
+    : binding_(this, std::move(request)) {}
+
+SensorProviderImpl::~SensorProviderImpl() {}
+
+namespace {

[Reilly Grant (use Gerrit), 2016/07/27 22:07:58]

nit: Keep all the functions defined in anonymous namespaces together at the top
of the file.

[Mikhail, 2016/08/09 19:38:28]

Done.

+
+void ReportError(const SensorProvider::GetSensorCallback& callback) {
+  callback.Run(nullptr, nullptr);
+}
+
+uint64_t GetBufferOffset(device::SensorType type) {
+  return (static_cast<uint64_t>(SensorType::LAST) -
+          static_cast<uint64_t>(type)) *
+         SensorReadBuffer::kReadBufferSize;
+}
+
+}  // namespace
+
+void SensorProviderImpl::GetSensor(device::SensorType type,
+                                   SensorRequest sensor_request,
+                                   const GetSensorCallback& callback) {
+  auto cloned_handle = s_provider_->GetClonedSharedBufferHandle();

[Reilly Grant (use Gerrit), 2016/07/27 22:07:58]

The use of auto in this function is counter to my expectations. I don't know
what the return value of GetClonedSharedBufferHandle() is here so I'd rather
have the type spelled out. In contrast, below when allocating a new SensorImpl
and SensorReadBuffer auto can be used because the type is already spelled out
once on that line.

[Mikhail, 2016/08/09 19:38:28]

Done.

+  if (!cloned_handle.is_valid()) {
+    ReportError(callback);
+    return;
+  }
+
+  auto sensor = s_provider_->GetSensor(type);
+  if (!sensor)

[Reilly Grant (use Gerrit), 2016/07/27 22:07:58]

nit: Braces are required around the body of a multi-line if.

[Mikhail, 2016/08/09 19:38:28]

Done.

+    sensor = s_provider_->CreateSensor(type, SensorReadBuffer::kReadBufferSize,
+                                       GetBufferOffset(type));
+  if (!sensor) {
+    ReportError(callback);
+    return;
+  }
+
+  SensorImpl* sensor_impl = new SensorImpl(std::move(sensor_request), sensor);
+
+  SensorReadBufferPtr sensor_read_buffer = SensorReadBuffer::New();
+  sensor_read_buffer->memory = std::move(cloned_handle);
+  sensor_read_buffer->offset = GetBufferOffset(type);
+  sensor_read_buffer->mode = sensor->GetReportingMode();
+
+  callback.Run(std::move(sensor_read_buffer), sensor_impl->GetClient());
+}
+
+}  // namespace mojom
+}  // namespace device