Create Memory Helper for memory warnings

ios/chrome/app/application_delegate/memory_warning_helper.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 IOS_CHROME_APP_APPLICATION_DELEGATE_MEMORY_RECOVERY_HELPER_H_
+#define IOS_CHROME_APP_APPLICATION_DELEGATE_MEMORY_RECOVERY_HELPER_H_
+
+#import <Foundation/Foundation.h>
+
+// Helper for handling memory warnings.
+@interface MemoryWarningHelper : NSObject
+
+// The number of memory warnings that have been received in this
+// foreground session.
+@property(nonatomic, readonly) NSInteger foregroundMemoryWarningCount;
+
+// Frees as much memory as possible and registers that there was a memory
+// pressure.
+- (void)handleMemoryPressure;
+
+// Resets the foregroundMemoryWarningCount property, setting its value to 0.
+- (void)resetForegroundMemoryWarningCount;
+
+@end
+
+#endif  // IOS_CHROME_APP_APPLICATION_DELEGATE_MEMORY_RECOVERY_HELPER_H_