Add a Mojo EDK for Chrome that uses one OS pipe per message pipe.

mojo/edk/system/simple_dispatcher.h

Index: mojo/edk/system/simple_dispatcher.h
diff --git a/third_party/mojo/src/mojo/edk/system/simple_dispatcher.h b/mojo/edk/system/simple_dispatcher.h
similarity index 89%
copy from third_party/mojo/src/mojo/edk/system/simple_dispatcher.h
copy to mojo/edk/system/simple_dispatcher.h
index a8284358bf7c9b1eb4f7a37c93597afec530f76a..ccef56433b8eb1b2f9495dd167d56e978e95bc5b 100644
--- a/third_party/mojo/src/mojo/edk/system/simple_dispatcher.h
+++ b/mojo/edk/system/simple_dispatcher.h
@@ -13,7 +13,7 @@
 #include "mojo/public/cpp/system/macros.h"
 
 namespace mojo {
-namespace system {
+namespace edk {
 
 // A base class for simple dispatchers. "Simple" means that there's a one-to-one
 // correspondence between handles and dispatchers (see the explanatory comment
@@ -25,8 +25,9 @@ class MOJO_SYSTEM_IMPL_EXPORT SimpleDispatcher : public Dispatcher {
   ~SimpleDispatcher() override;
 
   // To be called by subclasses when the state changes (so
-  // |GetHandleSignalsStateImplNoLock()| should be checked again).
-  void HandleSignalsStateChangedNoLock() MOJO_EXCLUSIVE_LOCKS_REQUIRED(mutex());
+  // |GetHandleSignalsStateImplNoLock()| should be checked again). Must be
+  // called under lock.
+  void HandleSignalsStateChangedNoLock();
 
   // |Dispatcher| protected methods:
   void CancelAllAwakablesNoLock() override;
@@ -38,12 +39,13 @@ class MOJO_SYSTEM_IMPL_EXPORT SimpleDispatcher : public Dispatcher {
                                 HandleSignalsState* signals_state) override;
 
  private:
-  AwakableList awakable_list_ MOJO_GUARDED_BY(mutex());
+  // Protected by |lock()|:
+  AwakableList awakable_list_;
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(SimpleDispatcher);
 };
 
-}  // namespace system
+}  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_SIMPLE_DISPATCHER_H_