Revert of Enable iPad Tab Switcher by default on iOS.

ios/chrome/browser/snapshots/snapshot_cache_internal.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_BROWSER_SNAPSHOTS_SNAPSHOT_CACHE_INTERNAL_H_
-#define IOS_CHROME_BROWSER_SNAPSHOTS_SNAPSHOT_CACHE_INTERNAL_H_
-
-#import "ios/chrome/browser/snapshots/snapshot_cache_internal.h"
-
-namespace base {
-class FilePath;
-}
-
-@class NSString;
-
-@interface SnapshotCache (Internal)
-// Returns filepath to the color snapshot of |sessionID|.
-+ (base::FilePath)imagePathForSessionID:(NSString*)sessionID;
-// Returns filepath to the greyscale snapshot of |sessionID|.
-+ (base::FilePath)greyImagePathForSessionID:(NSString*)sessionID;
-// Returns whether the snapshots are cached in a LRU cache.
-- (BOOL)usesLRUCache;
-// Returns whether the in-memory cache (as opposed to the on-disk cache) is
-// enabled.
-- (BOOL)inMemoryCacheIsEnabled;
-@end
-
-#endif  // IOS_CHROME_BROWSER_SNAPSHOTS_SNAPSHOT_CACHE_INTERNAL_H_