Update frame metrics / viewport when orientation changes

Sending zoom contraints update from TabChildHelper is delayed
until new target viewport size is calculated. The new target
viewport size is used for calculating minimum viewport size.

In addition, AsyncPanZoomController needs to reset also displayPort
when composition bounds have changed.
Add more framemetrics logging for AsyncPanZoomController
Add new LOG_FM macro for debugging frame metrics

Add "EmbedLiteViewPort:4" to NSPR_LOG_MODULES environment
variable to output frame metrics from embedlite.
Add window size related logs behind LOGT

Add "EmbedLiteTrace:4" to NSPR_LOG_MODULES environment
variable to see those.