Add |notify_client_on_reading_change| flag to sensor configuration

This is a CL following the discussion from:
https://codereview.chromium.org/2896583005/diff/180001/content/renderer/device_sensors/device_motion_event_pump.cc

When the sensor client sets its own timer to read the shared memory,
and the sensor reporting mode is ON_CHANGE, the sensor client gets
unnecessary high frequency SensorClient::SensorReadingChanged() mojo
IPC calls. This CL adds a |notify_client_on_reading_change| flag to
sensor configuration to fix it.

BUG=721427

Review-Url: https://codereview.chromium.org/2927263002
Cr-Commit-Position: refs/heads/master@{#479074}
6 files changed