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
Merge pull request #13394 from davidflanagan/bug915001v1.2

Merge pull request #13300 from davidflanagan/bug915001hd