GPII-175: Fixed the safari problem that pressing escape to hide discovery tool breaks the keyboard functionality of opening/closing the tool panel.
GPII-175: Use "event.preventDefault" rather than "return false" to prevent the pressDown event being fired several times at single escape press. This issue only happens in safari.
Merge branch 'master' into GPII-175
Merge remote-tracking branch 'cindy/GPII-175'

* cindy/GPII-175:
  GPII-175: Use "event.preventDefault" rather than "return false" to prevent the pressDown event being fired several times at single escape press. This issue only happens in safari.
  GPII-175: Fixed the safari problem that pressing escape to hide discovery tool breaks the keyboard functionality of opening/closing the tool panel.