Upstream Chrome on iOS source code [9/11].

ios/chrome/browser/ui/tab_switcher/tab_switcher_cache.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 IOS_CHROME_BROWSER_UI_TAB_SWITCHER_TAB_SWITCHER_CACHE_H_
+#define IOS_CHROME_BROWSER_UI_TAB_SWITCHER_TAB_SWITCHER_CACHE_H_
+
+#import <UIKit/UIKit.h>
+
+#import "ios/chrome/browser/tabs/tab_model_observer.h"
+
+@class Tab;
+
+typedef void (^SnapshotCompletionBlock)(UIImage*);
+
+struct PendingSnapshotRequest {
+  CFTimeInterval requestId;
+  NSUInteger sessionId;
+
+  PendingSnapshotRequest() : requestId(0), sessionId(0) {}
+
+  void clear() {
+    requestId = 0;
+    sessionId = 0;
+  }
+};
+
+// A class that provides access to resized snapshots of tabs. The snapshots are
+// cached and freed under memory pressure.
+@interface TabSwitcherCache : NSObject<TabModelObserver>
+
+@property(nonatomic, readonly) TabModel* mainTabModel;
+
+// Request a snapshot for the given |tab| of the given |size|, |completionBlock|
+// will be called with the requested snapshot. Must be called from the main
+// thread with a non nil |tab|, a non nil |completionBlock|, and a non
+// CGSizeZero |size|.
+// If the resized snapshot is cached, |completionBlock| is called synchronously.
+// Otherwise it is called asynchronously on the main thread. The block's
+// execution can be cancelled with |cancelPendingSnapshotRequest:|.
+// Requesting a snapshot for a given tab will cancel any previous request for
+// that same tab. The completion handler for a cancelled request may never be
+// called.
+- (PendingSnapshotRequest)requestSnapshotForTab:(Tab*)tab
+                                       withSize:(CGSize)size
+                                completionBlock:
+                                    (SnapshotCompletionBlock)completionBlock;
+
+// Updates the snapshot for the given |tab| with |image| resized to |size|.
+- (void)updateSnapshotForTab:(Tab*)tab
+                   withImage:(UIImage*)image
+                        size:(CGSize)size;
+
+// Cancels the request identified by |pendingRequest|. Does nothing if no
+// request matches |pendingRequest|.
+- (void)cancelPendingSnapshotRequest:(PendingSnapshotRequest)pendingRequest;
+
+// Sets the main and incognito tab models.
+- (void)setMainTabModel:(TabModel*)mainTabModel
+            otrTabModel:(TabModel*)otrTabModel;
+
+@end
+
+#endif  // IOS_CHROME_BROWSER_UI_TAB_SWITCHER_TAB_SWITCHER_CACHE_H_