[Sensors] Improvements in shared buffer managing

device/generic_sensor/platform_sensor_provider_base.cc

Index: device/generic_sensor/platform_sensor_provider_base.cc
diff --git a/device/generic_sensor/platform_sensor_provider_base.cc b/device/generic_sensor/platform_sensor_provider_base.cc
index 51c60ac5ae25e681cefa83ed2cdec325ee9d9ccc..80c2bfc103e7f4dfd66a8b796979609d6d2a61a9 100644
--- a/device/generic_sensor/platform_sensor_provider_base.cc
+++ b/device/generic_sensor/platform_sensor_provider_base.cc
@@ -14,7 +14,7 @@ namespace device {
 namespace {
 
 const uint64_t kSharedBufferSizeInBytes =
-    mojom::SensorInitParams::kReadBufferSize *
+    PlatformSensor::kReadingBufferSize *
     static_cast<uint64_t>(mojom::SensorType::LAST);
 
 }  // namespace
@@ -23,21 +23,19 @@ PlatformSensorProviderBase::PlatformSensorProviderBase() = default;
 PlatformSensorProviderBase::~PlatformSensorProviderBase() = default;
 
 scoped_refptr<PlatformSensor> PlatformSensorProviderBase::CreateSensor(
-    mojom::SensorType type,
-    uint64_t size,
-    uint64_t offset) {
+    mojom::SensorType type) {
   DCHECK(CalledOnValidThread());
 
   if (!CreateSharedBufferIfNeeded())
     return nullptr;
 
-  mojo::ScopedSharedBufferMapping mapping =
-      shared_buffer_handle_->MapAtOffset(size, offset);
+  mojo::ScopedSharedBufferMapping mapping = shared_buffer_handle_->MapAtOffset(
+      PlatformSensor::kReadingBufferSize, GetSharedBufferOffset(type));
   if (!mapping)
     return nullptr;
 
   scoped_refptr<PlatformSensor> new_sensor =
-      CreateSensorInternal(type, std::move(mapping), size);
+      CreateSensorInternal(type, std::move(mapping));
   if (!new_sensor)
     return nullptr;
 
@@ -83,4 +81,11 @@ PlatformSensorProviderBase::CloneSharedBufferHandle() {
   return shared_buffer_handle_->Clone();
 }
 
+uint64_t PlatformSensorProviderBase::GetSharedBufferOffset(
+    mojom::SensorType type) {
+  return (static_cast<uint64_t>(mojom::SensorType::LAST) -
+          static_cast<uint64_t>(type)) *
+         PlatformSensor::kReadingBufferSize;
+}
+
 }  // namespace device