Reland: Build Mojo apps in sub-dirs, like application packages.

mojo/runner/context.cc

Index: mojo/runner/context.cc
diff --git a/mojo/runner/context.cc b/mojo/runner/context.cc
index 57ee11dfc3a36fb07d7373487abd157ebc4603e3..c124529a621434bc6c012bbd51977949b52c2110 100644
--- a/mojo/runner/context.cc
+++ b/mojo/runner/context.cc
@@ -76,9 +76,9 @@ bool ConfigureURLMappings(const base::CommandLine& command_line,
   // The network service must be loaded from the filesystem.
   // This mapping is done before the command line URL mapping are processed, so
   // that it can be overridden.
-  resolver->AddURLMapping(
-      GURL("mojo:network_service"),
-      context->ResolveShellFileURL("file:network_service.mojo"));
+  resolver->AddURLMapping(GURL("mojo:network_service"),
+                          context->ResolveShellFileURL(
+                              "file:network_service/network_service.mojo"));
 
   // Command line URL mapping.
   std::vector<URLResolver::OriginMapping> origin_mappings =