Convert SetIsIncognitoProcess to use mojo.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 4e1eb8ca5d87a2c5d7ef77dd31e31ccb081d080c..d3d457c8c0b27bd8f71b09411446a132b43f98d5 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -1180,9 +1180,11 @@ void RenderThreadImpl::RemoveFilter(IPC::MessageFilter* filter) {
 
 void RenderThreadImpl::AddObserver(RenderThreadObserver* observer) {
   observers_.AddObserver(observer);
+  observer->RegisterMojoInterfaces(&associated_interfaces_);
 }
 
 void RenderThreadImpl::RemoveObserver(RenderThreadObserver* observer) {
+  observer->UnregisterMojoInterfaces(&associated_interfaces_);
   observers_.RemoveObserver(observer);
 }