NotForReview: Expose the global memory budget (chromium side)

base/memory/memory_coordinator_proxy.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_PROXY_H_
 #define BASE_MEMORY_MEMORY_COORDINATOR_PROXY_H_
 
 #include "base/base_export.h"
 #include "base/callback.h"
 #include "base/memory/memory_coordinator_client.h"
 #include "base/memory/singleton.h"
 
 namespace base {
 
 // The MemoryCoordinator interface. See comments in MemoryCoordinatorProxy for
 // method descriptions.
 class BASE_EXPORT MemoryCoordinator {
  public:
   virtual ~MemoryCoordinator() {}
 
   virtual MemoryState GetCurrentMemoryState() const = 0;
+  virtual int64_t GetGlobalBudget() = 0;
+  virtual void SetGlobalBudgetUpdateInterval(uint32_t interval_ms) = 0;
 };
 
 // The proxy of MemoryCoordinator to be accessed from components that are not
 // in content/browser e.g. net.
 class BASE_EXPORT MemoryCoordinatorProxy {
  public:
   static MemoryCoordinatorProxy* GetInstance();
 
   // Sets an implementation of MemoryCoordinator. MemoryCoordinatorProxy doesn't
   // take the ownership of |coordinator|. It must outlive this proxy.
   // This should be called before any components starts using this proxy.
   static void SetMemoryCoordinator(MemoryCoordinator* coordinator);
 
   // Returns the current memory state.
   MemoryState GetCurrentMemoryState() const;
 
+  // Returns the current global memory budget. A negative value can be returned
+  // if the global budget is unknown or the system is under high memory
+  // pressure.
+  int64_t GetGlobalBudget() const;
+
+  // TODO(bashi): Tentative.
+  void SetGlobalBudgetUpdateInterval(uint32_t interval_ms);
+
+  // Returns true when an instance of MemoryCoordinator is set.
+  bool IsEnabled();
+
  private:
   friend struct base::DefaultSingletonTraits<MemoryCoordinatorProxy>;
 
   MemoryCoordinatorProxy();
   virtual ~MemoryCoordinatorProxy();
 
   DISALLOW_COPY_AND_ASSIGN(MemoryCoordinatorProxy);
 };
 
 }  // namespace base
 
 #endif  // BASE_MEMORY_MEMORY_COORDINATOR_PROXY_H_