GM: include filename extension (.png) of each output file in JSON summary

GM: include filename extension (.png) of each output file in JSON summary

Doing this so that, once we *do* start writing PDF checksums into the JSON
summary, we'll be able to distinguish those from the PNG checksums.
Otherwise, we could have naming collisions.

R=scroggo@google.com

Committed: https://code.google.com/p/skia/source/detail?r=9119

[epoger, 2013-05-09 18:26:01]

https://codereview.chromium.org/14890017/diff/1/gm/gm.h
File gm/gm.h (right):

https://codereview.chromium.org/14890017/diff/1/gm/gm.h#newcode1
gm/gm.h:1: 
Patchset 1 just applies the diffs from
https://codereview.chromium.org/15014011/#ps10006 .

Not yet ready for review... I will be making changes as described in
https://codereview.chromium.org/15014011/diff/10006/gm/gm_expectations.cpp#ne...

[epoger, 2013-05-09 19:45:43]

Ready for review at patchset 2, which moves *all* of the file-extension adding
into gmmain.cpp.  Leave gm_expectations.cpp alone!!!

https://codereview.chromium.org/14890017/diff/3002/gm/gmmain.cpp
File gm/gmmain.cpp (right):

https://codereview.chromium.org/14890017/diff/3002/gm/gmmain.cpp#newcode127
gm/gmmain.cpp:127: const static char kPNG_FileExtension[] = "png";
Moved from gm_expectations.h into here, so that we know it isn't used in
gm_expectations.cpp anymore.

[epoger, 2013-05-09 20:06:57]

Ready for review at patchset 4, I promise this time.

https://codereview.chromium.org/14890017/diff/14001/gm/gm_expectations.cpp
File gm/gm_expectations.cpp (right):

https://codereview.chromium.org/14890017/diff/14001/gm/gm_expectations.cpp#ne...
gm/gm_expectations.cpp:38: result.appendUnichar(SkPATH_SEPARATOR);
Patchset 4 updates to work now that I have reverted my earlier addition of
SkString::append(const char)

[scroggo, 2013-05-13 15:05:43]

lgtm

[epoger, 2013-05-14 15:17:54]

Committed patchset #5 manually as r9119 (presubmit successful).