[content shell] use process-per-tab model
[content shell] use process-per-tab model

The test runner library which controls the layout test is instantiated in the
renderer. To make sure we're always using the same renderer, without resorting to
hacks, use the process-per-tab model. Running several layout tests in a row are
then guaranteed to all start in the same process.

Note that a layout test can still open a new window in a different process, but that
is already now supported

BUG=111316
TEST=running an https test after an http test does not time out
R=marja@chromium.org

Review URL: https://codereview.chromium.org/14066006

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@194334 0039d316-1c4b-4281-b951-d872f2087c98

markYoungH/chromium.src,krieger-od/nwjs_chromium.src,anirudhSK/chromium,ChromiumWebApps/chromium,crosswalk-project/chromium-crosswalk-efl,patrickm/chromium.src,hujiajie/pa-chromium,pozdnyakov/chromium-crosswalk,hgl888/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,TheTypoMaster/chromium-crosswalk,fujunwei/chromium-crosswalk,krieger-od/nwjs_chromium.src,chuan9/chromium-crosswalk,Just-D/chromium-1,jaruba/chromium.src,axinging/chromium-crosswalk,mogoweb/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,mogoweb/chromium-crosswalk,anirudhSK/chromium,ondra-novak/chromium.src,M4sse/chromium.src,ChromiumWebApps/chromium,hgl888/chromium-crosswalk,Fireblend/chromium-crosswalk,axinging/chromium-crosswalk,ondra-novak/chromium.src,littlstar/chromium.src,hgl888/chromium-crosswalk-efl,Jonekee/chromium.src,Just-D/chromium-1,mogoweb/chromium-crosswalk,bright-sparks/chromium-spacewalk,M4sse/chromium.src,hujiajie/pa-chromium,dushu1203/chromium.src,krieger-od/nwjs_chromium.src,Just-D/chromium-1,ltilve/chromium,crosswalk-project/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,jaruba/chromium.src,mogoweb/chromium-crosswalk,dednal/chromium.src,mogoweb/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,pozdnyakov/chromium-crosswalk,littlstar/chromium.src,anirudhSK/chromium,Chilledheart/chromium,ltilve/chromium,chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,ChromiumWebApps/chromium,pozdnyakov/chromium-crosswalk,patrickm/chromium.src,Chilledheart/chromium,dednal/chromium.src,dushu1203/chromium.src,ondra-novak/chromium.src,ondra-novak/chromium.src,bright-sparks/chromium-spacewalk,fujunwei/chromium-crosswalk,hujiajie/pa-chromium,pozdnyakov/chromium-crosswalk,hujiajie/pa-chromium,littlstar/chromium.src,hgl888/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,fujunwei/chromium-crosswalk,anirudhSK/chromium,Just-D/chromium-1,pozdnyakov/chromium-crosswalk,patrickm/chromium.src,mohamed--abdel-maksoud/chromium.src,Chilledheart/chromium,ChromiumWebApps/chromium,ChromiumWebApps/chromium,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,hujiajie/pa-chromium,PeterWangIntel/chromium-crosswalk,bright-sparks/chromium-spacewalk,PeterWangIntel/chromium-crosswalk,Chilledheart/chromium,mohamed--abdel-maksoud/chromium.src,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,mohamed--abdel-maksoud/chromium.src,littlstar/chromium.src,patrickm/chromium.src,dednal/chromium.src,ltilve/chromium,hgl888/chromium-crosswalk,anirudhSK/chromium,ltilve/chromium,hgl888/chromium-crosswalk-efl,PeterWangIntel/chromium-crosswalk,dednal/chromium.src,bright-sparks/chromium-spacewalk,Just-D/chromium-1,littlstar/chromium.src,pozdnyakov/chromium-crosswalk,bright-sparks/chromium-spacewalk,bright-sparks/chromium-spacewalk,dushu1203/chromium.src,mohamed--abdel-maksoud/chromium.src,crosswalk-project/chromium-crosswalk-efl,hgl888/chromium-crosswalk-efl,patrickm/chromium.src,Pluto-tv/chromium-crosswalk,ltilve/chromium,PeterWangIntel/chromium-crosswalk,dushu1203/chromium.src,hujiajie/pa-chromium,jaruba/chromium.src,Fireblend/chromium-crosswalk,M4sse/chromium.src,axinging/chromium-crosswalk,Jonekee/chromium.src,patrickm/chromium.src,dushu1203/chromium.src,jaruba/chromium.src,M4sse/chromium.src,ondra-novak/chromium.src,mohamed--abdel-maksoud/chromium.src,TheTypoMaster/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,ltilve/chromium,Fireblend/chromium-crosswalk,fujunwei/chromium-crosswalk,hgl888/chromium-crosswalk-efl,hujiajie/pa-chromium,ltilve/chromium,PeterWangIntel/chromium-crosswalk,anirudhSK/chromium,jaruba/chromium.src,pozdnyakov/chromium-crosswalk,M4sse/chromium.src,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,krieger-od/nwjs_chromium.src,jaruba/chromium.src,ltilve/chromium,jaruba/chromium.src,M4sse/chromium.src,Pluto-tv/chromium-crosswalk,fujunwei/chromium-crosswalk,anirudhSK/chromium,chuan9/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,fujunwei/chromium-crosswalk,dushu1203/chromium.src,chuan9/chromium-crosswalk,markYoungH/chromium.src,dednal/chromium.src,TheTypoMaster/chromium-crosswalk,Fireblend/chromium-crosswalk,hgl888/chromium-crosswalk-efl,krieger-od/nwjs_chromium.src,M4sse/chromium.src,mogoweb/chromium-crosswalk,mogoweb/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,jaruba/chromium.src,hujiajie/pa-chromium,markYoungH/chromium.src,dednal/chromium.src,M4sse/chromium.src,hujiajie/pa-chromium,axinging/chromium-crosswalk,krieger-od/nwjs_chromium.src,dednal/chromium.src,pozdnyakov/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,fujunwei/chromium-crosswalk,krieger-od/nwjs_chromium.src,Pluto-tv/chromium-crosswalk,hgl888/chromium-crosswalk-efl,hgl888/chromium-crosswalk,axinging/chromium-crosswalk,pozdnyakov/chromium-crosswalk,M4sse/chromium.src,bright-sparks/chromium-spacewalk,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,hgl888/chromium-crosswalk-efl,ltilve/chromium,chuan9/chromium-crosswalk,hgl888/chromium-crosswalk-efl,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