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
WebContentsFrameBindingSet<T>.

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.

BUG=612500

Review-Url: https://codereview.chromium.org/2310583002
Cr-Commit-Position: refs/heads/master@{#419259}
diff --git a/chrome/common/network_diagnostics.mojom b/chrome/common/network_diagnostics.mojom
new file mode 100644
index 0000000..8104e08
--- /dev/null
+++ b/chrome/common/network_diagnostics.mojom
@@ -0,0 +1,17 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+module mojom;
+
+import "url/mojo/url.mojom";
+
+interface NetworkDiagnostics {
+  RunNetworkDiagnostics(url.mojom.Url failed_url);
+};
+
+interface NetworkDiagnosticsClient {
+  // Tells the renderer whether or not there is a local diagnostics service that
+  // can be run via calls to NetworkDiagnostics::RunNetworkDiagnostics.
+  SetCanShowNetworkDiagnosticsDialog(bool can_show);
+};