Remove m_isContextElement
Remove m_isContextElement

r180614 forgot to remove m_isContextElement.

Review URL: https://codereview.chromium.org/488013002

git-svn-id: bf5cd6ccde378db821296732a091cfbcf5285fbd@180625 bbb929c8-8fbe-4397-9dbb-9b2b20218538

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk