memory coordinator: Add trace macros to track state changes

base/memory/memory_coordinator_client.cc

Index: base/memory/memory_coordinator_client.cc
diff --git a/base/memory/memory_coordinator_client.cc b/base/memory/memory_coordinator_client.cc
new file mode 100644
index 0000000000000000000000000000000000000000..7fa62321771fd440639b15993ddd750acc2fed77
--- /dev/null
+++ b/base/memory/memory_coordinator_client.cc
@@ -0,0 +1,27 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/memory/memory_coordinator_client.h"
+
+#include "base/logging.h"
+
+namespace base {
+
+const char* MemoryStateToString(MemoryState state) {
+  switch (state) {
+    case MemoryState::UNKNOWN:
+      return "unknown";
+    case MemoryState::NORMAL:
+      return "normal";
+    case MemoryState::THROTTLED:
+      return "throttled";
+    case MemoryState::SUSPENDED:
+      return "suspended";
+    default:
+      NOTREACHED();
+  }
+  return "";
+}
+
+}  // namespace base