Adds suppress_wildcard to gpu_tests_base
Without suppress_wildcard this target is included in All.gyp, which
results in All.gyp unnecessary including build/isolate.gypi and
getting a rule. If All has a rule then pretty much every change is
going to result in building All (on the bots).
AFAICT gpu_tests_base is only exposed as a base target for other test
targets in chrome_tests.gypi and not something All.gyp directly cares
about. The suppress_wildcard gives us this behavior.
BUG=chromium:500534
R=jmadill@chromium.org
Review URL: https://codereview.chromium.org/
1185753010
Cr-Commit-Position: refs/heads/master@{#334777}