In CanvasContext::doFrame, make a separate call to computeFrameTimeNanos

and save the result. Then pass that value to
UiFrameInfoBuilder::setVsync as both arguments.

The order of function argument evaluation is undefined in C++. Because
the value returned from TimeLord::latestVsync may be changed by
the preceding call to TimeLord::computeFrameTimeNanos the values of the
arguments passed to UiFrameInfoBuilder::setVsync is also undefined. This
change removes any ambiguity.

Change-Id: Ie71ee453f9ccc725edfe5f7cc9b277f2a809dfdc