Add ChildMemoryCoordinator::PurgeMemory()

content/child/memory/child_memory_coordinator_impl.h

Index: content/child/memory/child_memory_coordinator_impl.h
diff --git a/content/child/memory/child_memory_coordinator_impl.h b/content/child/memory/child_memory_coordinator_impl.h
index cee8d5a76054309f54ad86056a766a15d5262495..ccac9b4180371603651b52b1ac2e54c8b8684ae9 100644
--- a/content/child/memory/child_memory_coordinator_impl.h
+++ b/content/child/memory/child_memory_coordinator_impl.h
@@ -35,6 +35,9 @@ class CONTENT_EXPORT ChildMemoryCoordinatorImpl
                              ChildMemoryCoordinatorDelegate* delegate);
   ~ChildMemoryCoordinatorImpl() override;
 
+  // Requests purging memory to clients.
+  void PurgeMemory();
+
   // mojom::ChildMemoryCoordinator implementations:
   void OnStateChange(mojom::MemoryState state) override;