Add HandleScopes to V8DOMActivityLogger's methods

Since these V8DOMActivityLogger's methods can be called from core/
(not via bindings/), it makes sense to allocate a new HandleScope
in these methods.

BUG=411445
NOTRY=true

Review URL: https://codereview.chromium.org/559813002

git-svn-id: svn://svn.chromium.org/blink/trunk@181694 bbb929c8-8fbe-4397-9dbb-9b2b20218538