The application receives input events and produces graphic buffers in
response. We are interested in measuring the total time that the input
event takes to process, from the moment it's received on the device, to
the moment that the image is displayed on the screen.

To do this, we need to understand which input event produced a specific
buffer. In this CL, we are sending the input event id from FrameInfo to
SurfaceFlinger. This event id will later be used to identify a specific
frame, and provide the frame timing information to inputflinger.

Inputflinger will be able to use this information to reconstruct the
complete event timeline, and record metrics on the duration of each
input / graphics processing stage. This will allow us to optimize
end-to-end touch latency.

In the current CL, we are using 'NewestInputEvent' as the inputEventId.
That's not quite correct. Today, this field contains the timestamp of
the input event. Therefore, we will simply pass the truncated
timestamp instead of proper input event id. We will fix this in a
separate CL by providing input event id to FrameInfo.

Design doc: https://docs.google.com/document/d/1G3bLaZYSmbe6AKcL-6ZChvrw_B_LXEz29Z6Ed9QoYXY/edit#
Bug: 169866723
Test: printed input event id at the site of SurfaceFrame creation in
FrameTimeline.cpp

Change-Id: Ia90337bb2f000e9c93a4db04d9dd6ea9ea153520