Make it possible to remove an Awakable with a specific "context" from a Dispatcher.

mojo/edk/system/core_test_base.h

Index: mojo/edk/system/core_test_base.h
diff --git a/mojo/edk/system/core_test_base.h b/mojo/edk/system/core_test_base.h
index b828e768f5f3f4c0b5fa22a8edb8afe6c6f99a50..4bdaa6e2cd915a4e889d7f46003b5d915ddcb550 100644
--- a/mojo/edk/system/core_test_base.h
+++ b/mojo/edk/system/core_test_base.h
@@ -81,6 +81,7 @@ class CoreTestBase_MockHandleInfo {
   unsigned GetMapBufferCallCount() const;
   unsigned GetAddAwakableCallCount() const;
   unsigned GetRemoveAwakableCallCount() const;
+  unsigned GetRemoveAwakableWithContextCallCount() const;
   unsigned GetCancelAllStateCallCount() const;
 
   size_t GetAddedAwakableSize() const;
@@ -104,6 +105,7 @@ class CoreTestBase_MockHandleInfo {
   void IncrementMapBufferCallCount();
   void IncrementAddAwakableCallCount();
   void IncrementRemoveAwakableCallCount();
+  void IncrementRemoveAwakableWithContextCallCount();
   void IncrementCancelAllStateCallCount();
 
   void AllowAddAwakable(bool alllow);
@@ -129,6 +131,7 @@ class CoreTestBase_MockHandleInfo {
   unsigned map_buffer_call_count_ MOJO_GUARDED_BY(mutex_) = 0;
   unsigned add_awakable_call_count_ MOJO_GUARDED_BY(mutex_) = 0;
   unsigned remove_awakable_call_count_ MOJO_GUARDED_BY(mutex_) = 0;
+  unsigned remove_awakable_with_context_call_count_ MOJO_GUARDED_BY(mutex_) = 0;
   unsigned cancel_all_awakables_call_count_ MOJO_GUARDED_BY(mutex_) = 0;
 
   bool add_awakable_allowed_ MOJO_GUARDED_BY(mutex_) = false;