Add sequential dispatching for InitializationRunner

ios/chrome/app/deferred_initialization_runner.h

 // Copyright 2012 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_DEFERRED_INITIALIZATION_RUNNER_H_
 #define IOS_CHROME_APP_DEFERRED_INITIALIZATION_RUNNER_H_
 
 #import <Foundation/Foundation.h>
 
 #include "base/ios/block_types.h"
 
 // A singleton object to run initialization code asynchronously. Blocks are
 // scheduled to be run after a delay. The block is named when added to the
 // singleton so that other code can force a deferred block to be run
 // synchronously if necessary.
 @interface DeferredInitializationRunner : NSObject
 
 // Returns singleton instance.
 + (DeferredInitializationRunner*)sharedInstance;
 
+// Deprecated, use |enqueueBlockNamed:block:| instead.
 // Schedules |block| to be run after |delaySeconds| on the current queue.
 // This |block| is stored as |name| so code can force this initialization to
 // be run synchronously if necessary. This method may be called more than
 // once with the same |name| parameter. Any block with the same |name|
 // cancels a previously scheduled block of the same |name| if the block has
 // not been run yet.
 - (void)runBlockNamed:(NSString*)name
                 after:(NSTimeInterval)delaySeconds
                 block:(ProceduralBlock)block;
 
+// Stores |block| under |name| to a queue of blocks to run. All blocks are run
+// sequentially with a small delay before the first block and between each
+// successive block. If a block is already registered under |name|, it is
+// replaced with |block| unless it has already been run.
+- (void)enqueueBlockNamed:(NSString*)name block:(ProceduralBlock)block;
+
 // Looks up a previously scheduled block of |name|. If block has not been
 // run yet, run it synchronously now.
 - (void)runBlockIfNecessary:(NSString*)name;
 
 // Cancels a previously scheduled block of |name|. This is a no-op if the
 // block has already been executed.
 - (void)cancelBlockNamed:(NSString*)name;
 
 // Number of blocks that have been registered but not executed yet.
 // Exposed for testing.
 @property(nonatomic, readonly) NSUInteger numberOfBlocksRemaining;
 
 @end
 
+@interface DeferredInitializationRunner (ExposedForTesting)
+
+// Time interval between two blocks. Default value is 200ms.
+@property(nonatomic, assign) NSTimeInterval delayBetweenBlocks;
+
+// Time interval before running the first block. To override default value of
+// 3s, set this property before the first call to |-enqueueBlockNamed:block:|.
+@property(nonatomic, assign) NSTimeInterval delayBeforeFirstBlock;
+
+@end
+
 #endif  // IOS_CHROME_APP_DEFERRED_INITIALIZATION_RUNNER_H_