WIP: A couple of more ChannelMojo speedup ideas

third_party/mojo/src/mojo/edk/system/dispatcher.h

Index: third_party/mojo/src/mojo/edk/system/dispatcher.h
diff --git a/third_party/mojo/src/mojo/edk/system/dispatcher.h b/third_party/mojo/src/mojo/edk/system/dispatcher.h
index c069269b1a2bee1aae2eb5c94e2a20ce2857a2a6..a15bed197525ae1d6eb10c148188f0e52a4760b8 100644
--- a/third_party/mojo/src/mojo/edk/system/dispatcher.h
+++ b/third_party/mojo/src/mojo/edk/system/dispatcher.h
@@ -10,6 +10,7 @@
 
 #include <vector>
 
+#include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
@@ -42,6 +43,8 @@ class TransportData;
 class Awakable;
 
 typedef std::vector<scoped_refptr<Dispatcher>> DispatcherVector;
+typedef base::Callback<bool(const void* bytes, uint32_t num_bytes)>
+    AsyncMessageCallback;
 
 namespace test {
 
@@ -152,6 +155,8 @@ class MOJO_SYSTEM_IMPL_EXPORT Dispatcher
   // |*signals_state| will be set to the current handle signals state.
   void RemoveAwakable(Awakable* awakable, HandleSignalsState* signals_state);
 
+  MojoResult SetAsyncMessageCallback(const AsyncMessageCallback& callback);
+
   // A dispatcher must be put into a special state in order to be sent across a
   // message pipe. Outside of tests, only |HandleTableAccess| is allowed to do
   // this, since there are requirements on the handle table (see below).
@@ -274,6 +279,9 @@ class MOJO_SYSTEM_IMPL_EXPORT Dispatcher
   virtual void RemoveAwakableImplNoLock(Awakable* awakable,
                                         HandleSignalsState* signals_state);
 
+  virtual MojoResult SetAsyncMessageCallbackImplNoLock(
+      const AsyncMessageCallback& callback);
+
   // These implement the API used to serialize dispatchers to a |Channel|
   // (described below). They will only be called on a dispatcher that's attached
   // to and "owned" by a |MessageInTransit|. See the non-"impl" versions for