gm self-tests: stop comparing stdout/stderr/command_line, just look at JSON summary

gm/tests/outputs/add-config-pdf/output-expected/stdout

Index: gm/tests/outputs/add-config-pdf/output-expected/stdout
===================================================================
--- gm/tests/outputs/add-config-pdf/output-expected/stdout	(revision 10989)
+++ gm/tests/outputs/add-config-pdf/output-expected/stdout	(working copy)
@@ -1,19 +0,0 @@
-GM: These configs will be run: 8888 565 pdf
-GM: These PDF rasterizers will be run: poppler
-GM: reading expectations from JSON summary file gm/tests/inputs/json/identical-bytes.json
-GM: writing to gm/tests/outputs/add-config-pdf/output-actual/writePath
-GM: writing mismatches to gm/tests/outputs/add-config-pdf/output-actual/mismatchPath
-GM: writing images without expectations to gm/tests/outputs/add-config-pdf/output-actual/missingExpectationsPath
-GM: drawing... selftest1 [300 200]
-GM: Ran 1 GMs
-GM: ... over  3 configs ["8888", "565", "pdf"]

[epoger, 2013/08/28 19:43:04]

I'm disappointed we will no longer check this "header" info (which configs/modes
were run, and the "Ran 10 tests" line).  That seemed like a nice way to make
sure we were aware of any gm behavior changes.

Like, what if someone accidentally removes tilegrid from the list of default
modes to run, and later the tilegrid mode gets broken?  How would we find out? 
(The buildbots would not report any failures in any modes...)

-GM: ...  and  7 modes   ["pipe", "pipe cross-process", "pipe cross-process, shared address", "replay", "rtree", "serialize", "tilegrid"]
-GM: ... so there should be a total of 10 tests.
-GM: Ran 10 tests: NoGpuContext=0 IntentionallySkipped=0 RenderModeMismatch=0 ExpectationsMismatch=0 MissingExpectations=1 WritingReferenceImage=0
-GM: [*] 0 NoGpuContext:
-GM: [ ] 0 IntentionallySkipped:
-GM: [*] 0 RenderModeMismatch:
-GM: [*] 0 ExpectationsMismatch:
-GM: [ ] 1 MissingExpectations: pdf/selftest1
-GM: [*] 0 WritingReferenceImage:
-GM: (results marked with [*] will cause nonzero return value)