Implement device-ram client hints header

third_party/WebKit/Source/platform/MemoryCoordinator.h

 // Copyright 2015 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 MemoryCoordinator_h
 #define MemoryCoordinator_h
 
 #include "platform/PlatformExport.h"
 #include "platform/heap/Handle.h"
 #include "platform/wtf/Noncopyable.h"
@@ skipping 21 matching lines @@
     : public GarbageCollected<MemoryCoordinator> {
   WTF_MAKE_NONCOPYABLE(MemoryCoordinator);
 
  public:
   static MemoryCoordinator& Instance();
 
   // Whether the device Blink runs on is a low-end device.
   // Can be overridden in layout tests via internals.
   static bool IsLowEndDevice();
 
-  // Caches whether this device is a low-end device in a static member.
-  // instance() is not used as it's a heap allocated object - meaning it's not
-  // thread-safe as well as might break tests counting the heap size.
+  // Returns the amount of physical memory in megabytes on the device.
+  static int64_t GetPhysicalMemoryMB();
+
+  // Override the value of the physical memory for testing.
+  static void SetPhysicalMemoryMBForTesting(int64_t);
+
+  // Caches whether this device is a low-end device and the device physical
+  // memory in static members. instance() is not used as it's a heap allocated
+  // object - meaning it's not thread-safe as well as might break tests counting
+  // the heap size.
   static void Initialize();
 
   void RegisterClient(MemoryCoordinatorClient*);
   void UnregisterClient(MemoryCoordinatorClient*);
 
   // TODO(bashi): Deprecating. Remove this when MemoryPressureListener is
   // gone.
   void OnMemoryPressure(WebMemoryPressureLevel);
 
   void OnMemoryStateChange(MemoryState);
 
   void OnPurgeMemory();
 
   DECLARE_TRACE();
 
  private:
   friend class Internals;
 
   static void SetIsLowEndDeviceForTesting(bool);
 
   MemoryCoordinator();
 
   void ClearMemory();
 
   static bool is_low_end_device_;
+  static int64_t physical_memory_mb_;
 
   HeapHashSet<WeakMember<MemoryCoordinatorClient>> clients_;
 };
 
 }  // namespace blink
 
 #endif  // MemoryCoordinator_h