Bench baseline for mostly 0 image.

Bench baseline for mostly 0 image.

Add a baseline for decoding a mostly 0 image. This is in advance of
https://codereview.chromium.org/24269006/ which provides an option to
skip writing those 0s (as part of BUG=skia:1661). On my Nexus 4, the
benchmark does not slow down after that change.

As suggested in https://codereview.chromium.org/24269006/ add a
resourcePath flag to bench. Will require a change in buildbot in order
to actually use the flag.

Add an image used by the test.

Until https://codereview.chromium.org/24448002 is submitted,
the test will not actually be run by the bots (since it
won't know where to find the file).

BUG=skia:1661
R=djsollen@google.com, mtklein@google.com

Review URL: https://codereview.chromium.org/24440002

git-svn-id: http://skia.googlecode.com/svn/trunk@11461 2bbb7eff-a529-9590-31e7-b0007b416f81