Merge pull request #13300 from davidflanagan/bug915001hd

Bug 915001 - save edited images using tiles and display a progress bar r=hshih(cherry picked from commit d19550e2fb7331d5e4a54e8e998753378e7fd44a)

Conflicts:

	apps/gallery/index.html
	apps/gallery/js/ImageEditor.js

fix lint