Web content context menu shows over chrome://bookmarks menu.
Web content context menu shows over chrome://bookmarks menu.

Earlier 'contextmenu' event is getting passed to the background page and
due to this WebPage context menu is coming on top of menu button context menu.
Changes done so that 'contextmenu' event will get handled and not passed to background
page on similar lines as in context_menuu_handler.js file.

BUG=442200

Review URL: https://codereview.chromium.org/1088023003

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#326230}

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