Get test running scripts to detect and report common error.

Get test running scripts to detect and report common error.

testing/tools/run_corpus_tests.py assumes a debug build and will
fail cryptically if only a release build is available.

Arguably there shouldn't be a default because having one could lead
to accidentally running a stale version, but that is probably too
much of a change.

R=tsepez@chromium.org

Committed: https://pdfium.googlesource.com/pdfium/+/79569e74ddddb12b3a76d211d826be2a3d87d0d0

[brucedawson, 2015-05-20 22:59:19]

I finally tried running the test scripts, and hit a cryptic failure. I figured
it out but figured it would be nice to fail in a more helpful manner. Thoughts?

Obviously the same change should be made to all three of
run_{javascript,pixel,corpus}.

[Tom Sepez, 2015-05-20 23:24:38]

https://codereview.chromium.org/1150823003/diff/1/testing/tools/run_corpus_te...
File testing/tools/run_corpus_tests.py (right):

https://codereview.chromium.org/1150823003/diff/1/testing/tools/run_corpus_te...
testing/tools/run_corpus_tests.py:30: if not os.path.exists(pdfium_test_path):
This should move to line 49, so we do it once and not on every file to process.

https://codereview.chromium.org/1150823003/diff/1/testing/tools/run_corpus_te...
testing/tools/run_corpus_tests.py:32: print "Use --build-dir=out\\Release"
nit: there may be other build dirs besides just out/release, depending on how
clever the developer has been.  So maybe say
"Use the -build-dir option to search alternate locations"
or some such.

[brucedawson, 2015-05-20 23:30:34]

Good points. Moved, text changed, and fix applied to all three test runners.

PTAL.

[Tom Sepez, 2015-05-20 23:45:58]

lgtm

[brucedawson, 2015-05-20 23:52:13]

Committed patchset #2 (id:20001) manually as
79569e74ddddb12b3a76d211d826be2a3d87d0d0 (presubmit successful).