DevTools: protocol: add "canEmulateNetworkConditions" method definition.

BUG=396086

Review URL: https://codereview.chromium.org/456363002

git-svn-id: svn://svn.chromium.org/blink/trunk@179957 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Changes DOMDataStore's map type from DOMWrapperMap<void> to DOMWrapperMap<ScriptWrappableBase>.

BUG=235436

Review URL: https://codereview.chromium.org/460673002

git-svn-id: svn://svn.chromium.org/blink/trunk@179958 bbb929c8-8fbe-4397-9dbb-9b2b20218538