[WOCCatalog][ARM] Gestures: lines are only drawn after user lift fingers off the screen

[ArnOmsft]

• Open WOC Catalog Release or Debug
  -Tap Gestures
• Draw something on the screen using one or several fingers

Expected: blue lines showing the path drawed by each finger and a red line showing the resulting gesture (if multiple fingers have been used) should appear as the user is drawing
Result: the lines are drawn on the phone but only after the user lift off his finger(s) from the screen.

Note this bug is present on UX/UXE as well as \arcadiabuild03\Release\master\Release\20161102.1\drop\apps\x86\WOCCatalog_1.0.0.0_Win32_Test

[ArnOmsft]

From the original bug:

1. First draw is slow, and once starts, it seems draw in a burst.
2. If user continue to moving fingers after temporarily stop, if seems draw can not resume until user lift the finger.

From the trace, we are not blocking UIThread. But all the draw are pushed out to the end for some reason. Still needs a trace with symbols to find out the root cause.

[ms-jihua]

@ArnOmsft from your description "slow, draw in a burst", it's probably because of #1705, which batched draw calls to not execute until [CALayer display] exits. I'm not certain how gestures interact with the UI/CG draw stack, but I can take this over from @yiyang-msft if you think it'd be more appropriate for me to investigate.