DevTools: update histograms.xml with DevTools used statistics.
DevTools: update histograms.xml with DevTools used statistics.

The patch adds names for new DevTools.ActionTaken buckets.

It also fixes the PanelShown code 9: the "Extensions's panel" uma
value, in fact, was never used. We recently started recording "Layers"
panel with this code.

BUG=473838
R=pfeldman, dgozman

Review URL: https://codereview.chromium.org/1081213003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#325777}

hgl888/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Fireblend/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Just-D/chromium-1,Just-D/chromium-1,Fireblend/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,hgl888/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,chuan9/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,hgl888/chromium-crosswalk,chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Fireblend/chromium-crosswalk,Chilledheart/chromium,Chilledheart/chromium,Chilledheart/chromium,chuan9/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Just-D/chromium-1,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,hgl888/chromium-crosswalk,Just-D/chromium-1,Just-D/chromium-1,chuan9/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,axinging/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,hgl888/chromium-crosswalk,Chilledheart/chromium,Just-D/chromium-1,Fireblend/chromium-crosswalk,chuan9/chromium-crosswalk,axinging/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,chuan9/chromium-crosswalk,chuan9/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Chilledheart/chromium,hgl888/chromium-crosswalk,hgl888/chromium-crosswalk,axinging/chromium-crosswalk,Just-D/chromium-1,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,hgl888/chromium-crosswalk,chuan9/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Chilledheart/chromium,Just-D/chromium-1,axinging/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Fireblend/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Chilledheart/chromium,axinging/chromium-crosswalk,Chilledheart/chromium,PeterWangIntel/chromium-crosswalk,axinging/chromium-crosswalk,Pluto-tv/chromium-crosswalk,Chilledheart/chromium,TheTypoMaster/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,chuan9/chromium-crosswalk,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,Pluto-tv/chromium-crosswalk