Update comment on IOThread to point people to the right place if they

chrome/browser/io_thread.h

Index: chrome/browser/io_thread.h
diff --git a/chrome/browser/io_thread.h b/chrome/browser/io_thread.h
index 8a861cc3a76d09cfaa44c24592d72083e1a7e4f4..6a1f9f57a6c729970d821f9a5b1117b81dd69bc5 100644
--- a/chrome/browser/io_thread.h
+++ b/chrome/browser/io_thread.h
@@ -49,6 +49,10 @@ class URLSecurityManager;
 
 // Contains state associated with, initialized and cleaned up on, and
 // primarily used on, the IO thread.
+//
+// If you are looking to interact with the IO thread (e.g. post tasks
+// to it or check if it is the current thread), see
+// content::BrowserThread.
 class IOThread : public content::BrowserThreadDelegate {
  public:
   struct Globals {