fiddle: Fix caching of images.
fiddle: Fix caching of images.

BUG=skia:5339

Review-Url: https://codereview.chromium.org/2008663002

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot