Revert of x11/test: Use a custom-deleter for the stored XEvent. (https://codereview.chromium.org/136153006/)

Reason for revert:
This seems to cause leaks:
http://build.chromium.org/p/chromium.memory/builders/Linux%20ASAN%20Tests%20%282%29/builds/22514/steps/content_unittests/logs/TestMakeWebKeyboardEvent
http://build.chromium.org/p/chromium.memory/builders/Linux%20ASAN%20Tests%20%282%29/builds/22514/steps/content_unittests/logs/TestMakeWebKeyboardEventWindowsKeyCode

Original issue's description:
> x11/test: Use a custom-deleter for the XEvent in ScopedXI2Event.
> 
> BUG=none
> R=sky@chromium.org
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=248512

TBR=sky@chromium.org,sadrul@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=none

Review URL: https://codereview.chromium.org/135393011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248526 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248526