In  issue 616673  we are unifying all locations where ui::Event is converted to blink::WebInputEvent, and moving these to ui/events/blink.

Within content/browser/renderer_host/input/ there are a series of converters for other platform events:
  - web_input_event_builders_android
  - web_input_event_builders_mac

We should likely move these to ui/events/blink as well, and find duplicates throughout the codebase, like with ui::Event

Stretch would be to have each of the web_input_event_builder_* to share an api instead of only being similarly names.