DevTools: move front-end URL handling to DevToolsUIBindingds

BUG=662859

Review-Url: https://codereview.chromium.org/2607833002
Cr-Commit-Position: refs/heads/master@{#440926}
void DevToolsWindow::ContentsZoomChange(bool zoom_in) {
  DCHECK(is_docked_);
  zoom::PageZoom::Zoom(main_web_contents_, zoom_in ? content::PAGE_ZOOM_IN
                                                   : content::PAGE_ZOOM_OUT);
}

void DevToolsWindow::ContentsZoomChange(bool zoom_in) {
  DCHECK(is_docked_);
  zoom::PageZoom::Zoom(main_web_contents_, zoom_in ? content::PAGE_ZOOM_IN
                                                   : content::PAGE_ZOOM_OUT);
}
