Move NetworkService mojom files to content/public/common.

ipc/README.md

 # Converting Legacy Chrome IPC To Mojo
 
 Looking for [Mojo Documentation](/mojo)?
 
 [TOC]
 
 ## Overview
 
 The `//ipc` directory contains interfaces and implementation for Chrome's
 legacy IPC system, including `IPC::Channel` and various macros for defining
@@ skipping 586 matching lines @@
 module content.mojom;
 
 [Native]
 struct URLRequest;
 ```
 
 and add a typemap like [url_request.typemap](https://cs.chromium.org/chromium/src/content/common/url_request.typemap)
 to define the mapping:
 
 ```
-mojom = "//content/common/url_loader.mojom"
+mojom = "//content/public/common/url_loader.mojom"
 public_headers = [ "//content/common/resource_request.h" ]
 traits_headers = [ "//content/common/resource_messages.h" ]
 ...
 type_mappings = [ "content.mojom.URLRequest=content::ResourceRequest" ]
 ```
 
 Note specifically that `public_headers` includes the definition of the native
 C++ type, and `traits_headers` includes the definition of the legacy IPC traits.
 
 Finally, note that this same approach can be used to leverage existing
@@ skipping 41 matching lines @@
 [Chrome IPC to Mojo IPC Cheat Sheet](https://www.chromium.org/developers/design-documents/mojo/chrome-ipc-to-mojo-ipc-cheat-sheet)
 :    A slightly dated but still valuable document covering some details
      regarding the conceptual mapping between legacy IPC and Mojo.
 
 [Mojo Migration Guide](https://www.chromium.org/developers/design-documents/mojo/mojo-migration-guide)
 :    Another slightly (more) data document covering the basics of IPC conversion
      to Mojo.
 
      TODO: The migration guide above should probably be deleted and the good
      parts merged into this document.