Make SkPictureShader and SkPictureImageFilter use const SkPictures

Make SkPictureShader and SkPictureImageFilter use const SkPictures

TBR=reed@google.com

Committed: https://skia.googlesource.com/skia/+/e8464994bbcc797b47a5ee24aa513530d2bade3b

[mtklein, 2014-07-14 13:03:04]

lgtm

[robertphillips, 2014-07-14 13:51:12]

The CQ bit was checked by robertphillips@google.com

[commit-bot: I haz the power, 2014-07-14 13:51:33]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/robertphillips@google.com/390023002/1

[commit-bot: I haz the power, 2014-07-14 13:51:36]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-07-14 13:51:36]

Presubmit check for 390023002-1 failed and returned exit status 1.

Running presubmit commit checks ...

** Presubmit ERRORS **
Since the CL is editing public API, you must have an LGTM from one of:
('reed@chromium.org', 'reed@google.com', 'bsalomon@chromium.org',
'bsalomon@google.com')

Was the presubmit check useful? If not, run "git cl presubmit -v"
to figure out which PRESUBMIT.py was run, then run git blame
on the file to figure out who to ask for help.

[reed1, 2014-07-14 13:51:48]

lgtm

[reed1, 2014-07-14 13:51:56]

The CQ bit was checked by reed@google.com

[commit-bot: I haz the power, 2014-07-14 13:52:04]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/robertphillips@google.com/390023002/1

[commit-bot: I haz the power, 2014-07-14 14:53:31]

Change committed as e8464994bbcc797b47a5ee24aa513530d2bade3b