Convert some NetError[Tab]Helper messages to mojom

Converts ChromeViewHostMsg_RunNetworkDiagnostics and
ChromeViewMsg_SetCanShowNetworkDiagnosticsDialg to mojom without
impacting message ordering.

The browser-side interface is exposed via a

The renderer-side (client) interface is exposed via
RenderFrameImpl's AssociatedInterfaceRegistry.

This CL serves as a simple example of converting routed IPC
messages which are handled by WebContentsObservers or other
WebContents-bound things.


Cr-Commit-Position: refs/heads/master@{#419259}
8 files changed