memory coordinator: Add trace macros to track state changes

base/memory/memory_coordinator_client.h

Index: base/memory/memory_coordinator_client.h
diff --git a/base/memory/memory_coordinator_client.h b/base/memory/memory_coordinator_client.h
index d63b17cc1f8b88779dfaa83b7a677529dbc37573..7d4681eed0ab270bfc8b9f8b98139bb28ae9db84 100644
--- a/base/memory/memory_coordinator_client.h
+++ b/base/memory/memory_coordinator_client.h
@@ -38,6 +38,9 @@ enum class MemoryState {
   SUSPENDED = 2,
 };
 
+// Returns a string representation of MemoryState.
+BASE_EXPORT const char* MemoryStateToString(MemoryState state);
+
 // This is an interface for components which can respond to memory status
 // changes. An initial state is NORMAL. See MemoryCoordinatorClientRegistry for
 // threading guarantees and ownership management.