Change power key press to 0.2 secs.

There is an issue with nyan boards that power up but do not
enter recovery mode when the power button is pressed for less
than 0.2 secs.

BUG=chromium:394507
TEST=Ran tests against Big at desk

Change-Id: Ie049fed170cc3e550f9fa616bcc88d2ddb007c11
Reviewed-on: https://chromium-review.googlesource.com/214824
Reviewed-by: shikha shrivastava <shikhas@nvidia.com>
Tested-by: shikha shrivastava <shikhas@nvidia.com>
Reviewed-by: danny chan <dchan@chromium.org>
Commit-Queue: Yusuf Mohsinally <mohsinally@chromium.org>
Tested-by: Yusuf Mohsinally <mohsinally@chromium.org>
diff --git a/servo/keyboard_handlers.py b/servo/keyboard_handlers.py
index 70ed386..83f7fbd 100644
--- a/servo/keyboard_handlers.py
+++ b/servo/keyboard_handlers.py
@@ -27,7 +27,7 @@
     # existing platforms, but if this code is to be used for
     # qualification of new hardware, we should be less generous.
     LONG_DELAY = 8.5
-    SHORT_DELAY = 0.1
+    SHORT_DELAY = 0.2
     NORMAL_TRANSITION_DELAY = 1.2
 
     # Maximum number of times to re-read power button on release.