Temporarily increase retry limit in test_launcher
Temporarily increase retry limit in test_launcher

In bot mode, test_launcher would normally retry tests up to 3 times.
This is sufficient to keep large test suites like browser_tests under
1% flakiness rate if the flakiness of individual tests is also within
1%. However, some tests especially in browser_tests are up to 33%
flaky, making the browser_tests suite 40% flaky.

Subsequent top-level retries effectively double the runtime of all
bots running these tests, and we need a solution to shorten the try
job runtime.

A longer-term solution is the ignorer bot (see the bug), but until
it's deployed, a quick hack is to increase the number of retries so
statistically we should see about 1% flakiness of browser_tests at the
expense of a slight runtime increase.

R=sergiyb@chromium.org
BUG=390600, 395189

Review URL: https://codereview.chromium.org/393283006

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@284650 0039d316-1c4b-4281-b951-d872f2087c98

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oud/chromium.src,hgl888/chromium-crosswalk-efl,PeterWangIntel/chromium-crosswalk,chuan9/chromium-crosswalk,bright-sparks/chromium-spacewalk,littlstar/chromium.src,TheTypoMaster/chromium-crosswalk,M4sse/chromium.src,krieger-od/nwjs_chromium.src,mohamed--abdel-maksoud/chromium.src,crosswalk-project/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,crosswalk-project/chromium-crosswalk-efl,TheTypoMaster/chromium-crosswalk,dushu1203/chromium.src,crosswalk-project/chromium-crosswalk-efl,dednal/chromium.src,jaruba/chromium.src,Just-D/chromium-1,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,dednal/chromium.src,mohamed--abdel-maksoud/chromium.src,ltilve/chromium,Fireblend/chromium-crosswalk,jaruba/chromium.src,krieger-od/nwjs_chromium.src,dushu1203/chromium.src,mohamed--abdel-maksoud/chromium.src,markYoungH/chromium.src,axinging/chromium-crosswalk,Just-D/chromium-1,dushu1203/chromium.src,krieger-od/nwjs_chromium.src,ondra-novak/chromium.src,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,axinging/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,dushu1203/chromium.src