Revert of Make RenderProcessHost/RenderThread use MojoChildConnection/MojoShellConnection

content/public/test/mock_render_thread.cc

Index: content/public/test/mock_render_thread.cc
diff --git a/content/public/test/mock_render_thread.cc b/content/public/test/mock_render_thread.cc
index 3049984b4b4fbc950d3ad4330f1fdbdd1aba0381..90c55d732aad616ef10b0eaefbfe9904f3731235 100644
--- a/content/public/test/mock_render_thread.cc
+++ b/content/public/test/mock_render_thread.cc
@@ -184,10 +184,6 @@
 
 #endif  // OS_WIN
 
-MojoShellConnection* MockRenderThread::GetMojoShellConnection() {
-  return nullptr;
-}
-
 shell::InterfaceRegistry* MockRenderThread::GetInterfaceRegistry() {
   if (!interface_registry_)
     interface_registry_.reset(new shell::InterfaceRegistry(nullptr));