Faster GPU rect blur that doesn't require computing vertical and horizontal

Faster GPU rect blur that doesn't require computing vertical and horizontal
scanlines on the CPU first.  Should make extremely large drop shadows fast
again.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/fe689c46a764ded343e5028f79ead80c8b140b0f

[humper, 2014-06-05 19:51:41]

ptal.  All GM changes are extremely minimal imperceptible noise.

[bsalomon, 2014-06-05 20:29:18]

lgtm

https://codereview.chromium.org/316273004/diff/1/src/effects/SkBlurMaskFilter...
File src/effects/SkBlurMaskFilter.cpp (right):

https://codereview.chromium.org/316273004/diff/1/src/effects/SkBlurMaskFilter...
src/effects/SkBlurMaskFilter.cpp:715: key.fData32[1] = 1;
you could just delete this line (the key is memset to 0 two lines up)

[humper, 2014-06-06 13:26:33]

The CQ bit was checked by humper@google.com

[commit-bot: I haz the power, 2014-06-06 13:27:09]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/humper@google.com/316273004/1

[commit-bot: I haz the power, 2014-06-06 14:09:55]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  Build-Win7-VS2010-x86-Debug-Trybot on tryserver.chromium
(http://108.170.220.76:10117/builders/Build-Win7-VS2010-x86-Debug-Trybot/build...)

[humper, 2014-06-06 14:30:45]

The CQ bit was checked by humper@google.com

[commit-bot: I haz the power, 2014-06-06 14:30:55]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/humper@google.com/316273004/20001

[commit-bot: I haz the power, 2014-06-06 15:12:15]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  Build-Win7-VS2010-x86-Debug-Trybot on tryserver.chromium
(http://108.170.220.76:10117/builders/Build-Win7-VS2010-x86-Debug-Trybot/build...)

[commit-bot: I haz the power, 2014-06-06 15:22:15]

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

[commit-bot: I haz the power, 2014-06-06 15:22:16]

Try jobs failed on following builders:
  Build-Win7-VS2010-x86-Debug-Trybot on tryserver.chromium
(http://108.170.220.76:10117/builders/Build-Win7-VS2010-x86-Debug-Trybot/build...)

[humper, 2014-06-06 16:22:45]

The CQ bit was checked by humper@google.com

[commit-bot: I haz the power, 2014-06-06 16:23:26]

CQ is trying da patch. Follow status at
 https://skia-tree-status.appspot.com/cq/humper@google.com/316273004/40001

[commit-bot: I haz the power, 2014-06-06 16:48:43]

Change committed as fe689c46a764ded343e5028f79ead80c8b140b0f

[jvanverth1, 2014-06-06 18:01:46]

A revert of this CL has been created in
https://codereview.chromium.org/320563003/ by jvanverth@google.com.

The reason for reverting is: Many tree failures in RunTests (looks like
GLProgramsTest)..