Move memory_coordinator_client and its registry to base/memory

base/memory/memory_coordinator_client.h

+// 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.
+
+#ifndef BASE_MEMORY_MEMORY_COORDINATOR_CLIENT_H_
+#define BASE_MEMORY_MEMORY_COORDINATOR_CLIENT_H_
+
+#include "base/base_export.h"
+
+namespace base {
+
+// MemoryState represents status of a process.

[dcheng, 2016/09/15 00:19:19]

Btw, not sure if you want to update these comments or not (since I think they're
a bit different in the mojom)

[bashi, 2016/09/15 00:28:13]

Yeah, I'll update the comments to refer .mojom

[bashi, 2016/09/15 00:39:39]

Moved comments from
components/memory_coordinator/public/interfaces/child_memory_coordinator.mojom
to here.

+enum class MemoryState {
+  // The state is unknown.
+  UNKNOWN = -1,
+  // Not encountering memory constrains.
+  NORMAL = 0,
+  // Running and interactive but allocations may be limited.
+  THROTTLED = 1,
+  // Still in resident memory but its core processing logic has been suspended.
+  SUSPENDED = 2,
+};
+
+// This is an interface for components which can respond to memory status
+// changes.
+class BASE_EXPORT MemoryCoordinatorClient {
+ public:
+  virtual ~MemoryCoordinatorClient() {}
+
+  // Called when memory state has changed.
+  virtual void OnMemoryStateChange(MemoryState state) = 0;
+};
+
+}  // namespace base
+
+#endif  // BASE_MEMORY_MEMORY_COORDINATOR_CLIENT_H_