Add option to ignore small pixel diffs for --validate. By default, right

Add option to ignore small pixel diffs for --validate. By default, right
now we will default to max diff of 256, which means that for now we
report all pixels that are not as expected and we do not error out.
Ideally we will decrease the value of max diff to something that does
not have visual impact, e.g. 10, then we will report small changes with
the intensity under 10, but we will error out for anything larger.
Committed: https://code.google.com/p/skia/source/detail?r=7232

[reed1, 2013-01-16 16:06:39]

https://codereview.appspot.com/7137046/diff/1/tools/render_pictures_main.cpp
File tools/render_pictures_main.cpp (right):

https://codereview.appspot.com/7137046/diff/1/tools/render_pictures_main.cpp#...
tools/render_pictures_main.cpp:178: 
SkMax32 already exists

https://codereview.appspot.com/7137046/diff/1/tools/render_pictures_main.cpp#...
tools/render_pictures_main.cpp:180: 
The caller is not passing SkColor, but SkPMColor.

[edisonn, 2013-01-16 16:52:29]

https://codereview.appspot.com/7137046/diff/1/tools/render_pictures_main.cpp
File tools/render_pictures_main.cpp (right):

https://codereview.appspot.com/7137046/diff/1/tools/render_pictures_main.cpp#...
tools/render_pictures_main.cpp:178: 
On 2013/01/16 16:06:41, reed1 wrote:
> SkMax32 already exists

Done.

https://codereview.appspot.com/7137046/diff/1/tools/render_pictures_main.cpp#...
tools/render_pictures_main.cpp:180: 
On 2013/01/16 16:06:41, reed1 wrote:
> The caller is not passing SkColor, but SkPMColor.

used getByte generic function

[reed1, 2013-01-16 17:50:41]

lgtm