Fixes leak in BackingStore as shown by valgrind. XFree doesn't free the data of the image, where as XDestroyImage does.
Fixes leak in BackingStore as shown by valgrind. XFree doesn't free
the data of the image, where as XDestroyImage does.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/386003

git-svn-id: http://src.chromium.org/svn/trunk/src@31699 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: f40897473a1a014476e8b458bea5add0613dc121
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser