metrics: Add UpdateEngine.SuccessfulUpdate.* metrics.
metrics: Add UpdateEngine.SuccessfulUpdate.* metrics.

We've rewritten the metrics reported by the ChromeOS update_engine.
It's done in a way so the new metrics (UpdateEngine.*) will live
alongside the with the existing metrics (Installer.*). We plan to
eventually remove the old metrics.

This CL adds metrics in the UpdateEngine.SuccessfulUpdate.*
namespace. Many of these new metrics correspond - but are not 100%
identical - to the existing metrics in the Installer.* namespace.

BUG=chromium:355745
TEST=Validated the xml, pretty print succeeded.
R=asvitkine@chromium.org, avakulenko@chromium.org, deymo@chromium.org, isherman@chromium.org, jar@chromium.org, sosa@chromium.org

Review URL: https://codereview.chromium.org/227663004

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@262632 0039d316-1c4b-4281-b951-d872f2087c98

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kYoungH/chromium.src,ltilve/chromium,jaruba/chromium.src,dushu1203/chromium.src,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,hgl888/chromium-crosswalk,dednal/chromium.src,Fireblend/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,PeterWangIntel/chromium-crosswalk,markYoungH/chromium.src,dednal/chromium.src,littlstar/chromium.src,axinging/chromium-crosswalk,crosswalk-project/chromium-crosswalk-efl,krieger-od/nwjs_chromium.src,hgl888/chromium-crosswalk,ondra-novak/chromium.src,dednal/chromium.src,markYoungH/chromium.src,dushu1203/chromium.src,markYoungH/chromium.src,M4sse/chromium.src,Jonekee/chromium.src,fujunwei/chromium-crosswalk,Jonekee/chromium.src,crosswalk-project/chromium-crosswalk-efl,bright-sparks/chromium-spacewalk,hgl888/chromium-crosswalk,littlstar/chromium.src,dednal/chromium.src,ltilve/chromium,mohamed--abdel-maksoud/chromium.src,littlstar/chromium.src,krieger-od/nwjs_chromium.src,Fireblend/chromium-crosswalk,M4sse/chromium.src,mohamed--abdel-maksoud/chromium.src,jaruba/chromium.src,krieger-od/nwjs_chromium.src,TheTypoMaster/chromium-crosswalk