memory coordinator: Introduce MemoryCoordinatorImpl::Policy

content/browser/memory/memory_coordinator_default_policy.h

Index: content/browser/memory/memory_coordinator_default_policy.h
diff --git a/content/browser/memory/memory_coordinator_default_policy.h b/content/browser/memory/memory_coordinator_default_policy.h
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index 0000000000000000000000000000000000000000..599b964d428e2e36895dc60c95a6bdcd77254252
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+++ b/content/browser/memory/memory_coordinator_default_policy.h
@@ -0,0 +1,43 @@
+// Copyright 2017 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 CONTENT_BROWSER_MEMORY_MEMORY_COORDINATOR_DEFAULT_POLICY_H_
+#define CONTENT_BROWSER_MEMORY_MEMORY_COORDINATOR_DEFAULT_POLICY_H_
+
+#include "content/browser/memory/memory_coordinator_impl.h"
+
+namespace content {
+
+// The default policy of MemoryCoordinator.
+class MemoryCoordinatorDefaultPolicy : public MemoryCoordinatorImpl::Policy {
+ public:
+  explicit MemoryCoordinatorDefaultPolicy(MemoryCoordinatorImpl* coordinator);
+  ~MemoryCoordinatorDefaultPolicy() override;
+
+  void OnWarningCondition() override;
+  void OnCriticalCondition() override;
+  void OnConditionChanged(MemoryCondition prev, MemoryCondition next) override;
+  void OnChildVisibilityChanged(int render_process_id,
+                                bool is_visible) override;
+
+ private:
+  // Set the provided memory_state to all child processes.
+  void SetMemoryStateToAllChildren(MemoryState memory_state);
+
+  enum class PurgeTarget {
+    BACKGROUNDED,
+    ALL,
+  };
+
+  // Tries to find a candidate child process for purging memory and asks the
+  // child to purge memory.
+  bool TryToPurgeMemoryFromChildren(PurgeTarget target);
+
+  // Not owned.
+  MemoryCoordinatorImpl* coordinator_;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_MEMORY_MEMORY_COORDINATOR_DEFAULT_POLICY_H_