Implement basic mojo Permission service and use it for Geolocation.

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 84a31ba849001026b451f344c400dacf2965db3a..464dbbc043de5938deebfeb360fa71caabc57e2d 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -66,6 +66,8 @@
 #include "content/browser/mime_registry_message_filter.h"
 #include "content/browser/mojo/mojo_application_host.h"
 #include "content/browser/notifications/notification_message_filter.h"
+#include "content/browser/permissions/permission_service_context.h"
+#include "content/browser/permissions/permission_service_impl.h"
 #include "content/browser/profiler_message_filter.h"
 #include "content/browser/push_messaging/push_messaging_message_filter.h"
 #include "content/browser/quota_dispatcher_host.h"
@@ -875,6 +877,12 @@ void RenderProcessHostImpl::CreateMessageFilters() {
 void RenderProcessHostImpl::RegisterMojoServices() {
   mojo_application_host_->service_registry()->AddService(
       base::Bind(&device::BatteryMonitorImpl::Create));
+
+  scoped_ptr<PermissionServiceContext> permission_service_context(
+    new PermissionServiceContext(nullptr));

[nasko, 2014/11/13 23:57:38]

Why is it valid to register a context with null RFH?

[mlamouri (slow - plz ping), 2014/11/14 00:16:33]

The service on the RenderProcessHost can't show any UI (RFH is needed for that)
but we still want a service to be available for the rest of the features it
provides.

I've decided to pass a null RFH so the service always have a context but will
have to check whether its context has a RFH/WebContents. Does that sound sane to
you? Alternatively, I could pass a null context.

[nasko, 2014/11/14 00:42:50]

I like always having a context and it including the indicators on how it should
be used. I think what you have here is fine, it was more of me trying to get the
bigger picture of how this works.

+  mojo_application_host_->service_registry()->AddService(
+      base::Bind(&PermissionServiceImpl::Create,
+                 base::Passed(&permission_service_context)));
 }
 
 int RenderProcessHostImpl::GetNextRoutingID() {