add open devtools api to webview tag
update and document openDevTools on web view.
fix for cpplint
force devtools to show as undocked.
Merge branch 'webview-devtools' of https://github.com/project-infinium/atom-shell into project-infinium-webview-devtools
Fix double freeing WebContents
Show devtools for guest page in undocked mode
Also add closeDevTools and isDevToolsOpened for webview
Fix JavaScript errors in webview
Merge pull request #778 from atom/project-infinium-webview-devtools

devtools for webview tags (continue work of #774)