[Sensors] Improvements in shared buffer managing

device/generic_sensor/public/interfaces/sensor_provider.mojom

Index: device/generic_sensor/public/interfaces/sensor_provider.mojom
diff --git a/device/generic_sensor/public/interfaces/sensor_provider.mojom b/device/generic_sensor/public/interfaces/sensor_provider.mojom
index b7e4d2b9caaa6e6ff6b30255165adefece7a4b28..06eb7cbbdb34e76da4796e2de3af7ca27b7d3ff8 100644
--- a/device/generic_sensor/public/interfaces/sensor_provider.mojom
+++ b/device/generic_sensor/public/interfaces/sensor_provider.mojom
@@ -19,10 +19,10 @@ struct SensorInitParams {
   // Default sensor configuration.
   SensorConfiguration default_configuration;
 
-  // Note: Each sensor's read buffer contains 4 tightly packed 64-bit floating
-  // point fields, its layout is: { double timestamp; double values[3] }.
-  // So it has a fixed size 4*8 = 32 bytes.
-  const uint64 kReadBufferSize = 32;
+  // Each sensor's read buffer contains 4 tightly packed 64-bit floating
+  // point fields (please see sensor_reading.h) and a seqlock, so its size is
+  // 5 * 8 = 40 bytes.
+  const uint64 kReadBufferSizeForTests = 40;
 };
 
 interface SensorProvider {