[build] import closure_compiler V20141120.
[evita] ui: Call |ui::Widget::WillDestroyWidget()| in |ui::Widget::WillDestroyNaitiveWidget()|.
[evita] dom: Print evita version and V8 version at JS console start up.
[evita] dom: Stop using JS Minifier to support ES6 template string.
[evita] dom/lexers: Support JavaScript template string syntax, e.g. `this is ${foo}`.