Make mojo::system::Core not own the PlatformSupport.

mojo/edk/system/channel.h

Index: mojo/edk/system/channel.h
diff --git a/mojo/edk/system/channel.h b/mojo/edk/system/channel.h
index 46ffb6b77fdeed768c0e36b7fbb615950badf284..93ba87ae95743ec56b7b4ec91a1a4c766a8f1c89 100644
--- a/mojo/edk/system/channel.h
+++ b/mojo/edk/system/channel.h
@@ -54,8 +54,7 @@ class MOJO_SYSTEM_IMPL_EXPORT Channel
     : public base::RefCountedThreadSafe<Channel>,
       public RawChannel::Delegate {
  public:
-  // |platform_support| (typically owned by |Core|) must remain alive until
-  // after |Shutdown()| is called.
+  // |platform_support| must remain alive until after |Shutdown()| is called.
   explicit Channel(embedder::PlatformSupport* platform_support);
 
   // This must be called on the creation thread before any other methods are