ash: Add basic prediction code to the laser pointer.

ash/common/ash_switches.cc

Index: ash/common/ash_switches.cc
diff --git a/ash/common/ash_switches.cc b/ash/common/ash_switches.cc
index d1546b1b73abfb52f7cd28526004ad24a8b3179f..71275fddd16f1e64bb945a24ba79d2151e813603 100644
--- a/ash/common/ash_switches.cc
+++ b/ash/common/ash_switches.cc
@@ -65,6 +65,10 @@ const char kAshEnableTouchView[] = "enable-touchview";
 // Enables mirrored screen.
 const char kAshEnableMirroredScreen[] = "ash-enable-mirrored-screen";
 
+// Specifies the estimated time (in milliseconds) from VSYNC event until when

[Daniele Castagna, 2017/03/15 19:07:28]

Wouldn't this be the estimated time from when you write to the buffer until when
the pixel can be seen by the user?

[reveman, 2017/03/16 12:57:28]

No, that's not the idea. The usage of this in chrome might add additional
latency based on next vsync time if it wants to be really accurate but this
should not be set to a higher value to compensate for delta between buffer
update and vsync as that's something only chrome can do accurately at run time.

+// visible light can be noticed by the user.
+const char kAshEstimatedPresentationDelay[] = "estimated-presentation-delay";
+
 // Enables the palette next to the status area.
 const char kAshForceEnablePalette[] = "ash-force-enable-palette";