Add sequential dispatching for InitializationRunner

ios/chrome/app/deferred_initialization_runner.h

Index: ios/chrome/app/deferred_initialization_runner.h
diff --git a/ios/chrome/app/deferred_initialization_runner.h b/ios/chrome/app/deferred_initialization_runner.h
index e1bd59ce5e9006bb2fed80ffb1fd0202fc852000..d8c4fa5ebb4203194337d53e160edcef399e66be 100644
--- a/ios/chrome/app/deferred_initialization_runner.h
+++ b/ios/chrome/app/deferred_initialization_runner.h
@@ -18,6 +18,7 @@
 // Returns singleton instance.
 + (DeferredInitializationRunner*)sharedInstance;
 
+// Deprecated.
 // 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
@@ -28,6 +29,16 @@
                 after:(NSTimeInterval)delaySeconds
                 block:(ProceduralBlock)block;
 
+// Adds |block| to a block queue containing all block not run. The blocks in the
+// queue are runned sequentially with a small delay between each block.
+// If the queue is empty |block| is run after a small delay.
+// 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)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;