[mojo-edk] Expose notification source to MojoWatch callbacks

mojo/edk/system/wait_set_dispatcher_unittest.cc

Index: mojo/edk/system/wait_set_dispatcher_unittest.cc
diff --git a/mojo/edk/system/wait_set_dispatcher_unittest.cc b/mojo/edk/system/wait_set_dispatcher_unittest.cc
index a90a35604060e8212d39e510eb4f28b34c52c5b0..2a42be164523a718a506bcfb3434061b47099145 100644
--- a/mojo/edk/system/wait_set_dispatcher_unittest.cc
+++ b/mojo/edk/system/wait_set_dispatcher_unittest.cc
@@ -14,6 +14,7 @@
 #include "mojo/edk/embedder/embedder_internal.h"
 #include "mojo/edk/system/core.h"
 #include "mojo/edk/system/message_pipe_dispatcher.h"
+#include "mojo/edk/system/request_context.h"
 #include "mojo/edk/system/test_utils.h"
 #include "mojo/edk/system/waiter.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -78,6 +79,10 @@ class WaitSetDispatcherTest : public ::testing::Test {
   scoped_refptr<MessagePipeDispatcher> dispatcher1_;
 
  private:
+  // We keep an active RequestContext for the duration of each test. It's unused
+  // since these tests don't rely on the MojoWatch API.
+  const RequestContext request_context_;
+
   static uint64_t pipe_id_generator_;
   DispatcherVector dispatchers_to_close_;