Introduce optimized Timer.run queue for immediate runs.

sdk/lib/async/timer.dart

Index: sdk/lib/async/timer.dart
diff --git a/sdk/lib/async/timer.dart b/sdk/lib/async/timer.dart
index 39fe4c2df6202e1500940372e47d2583085f16b8..7df5e6cbdc1840825a121196643d1e7bc448e019 100644
--- a/sdk/lib/async/timer.dart
+++ b/sdk/lib/async/timer.dart
@@ -5,6 +5,9 @@
 part of dart.async;
 
 abstract class Timer {
+  // Internal queue used to group Timer.run callbacks.
+  static Queue _queue = new Queue();

[floitsch, 2013/02/25 16:07:13]

A list is good enough.

[Anders Johnsen, 2013/02/25 16:25:18]

Done.

+
   /**
    * Creates a new timer.
    *
@@ -51,8 +54,19 @@ abstract class Timer {
    * Returns a [Timer] that can be cancelled if the callback is not necessary

[floitsch, 2013/02/25 16:07:13]

Update comment.

[Anders Johnsen, 2013/06/11 12:14:31]

Done.

    * anymore.
    */
-  static Timer run(void callback()) {
-    return new Timer(const Duration(), callback);
+  static void run(void callback()) {

[Søren Gjesse, 2013/02/25 16:00:38]

I don't see any problem with this not having any object associated for canceling
it. It is run "almost immediately" so the cancellation window is short and would
most likely have to use some knowledge about the order of execution if one
Timer.run function should be cancelled from another Tumer.run function.

[Anders Johnsen, 2013/02/25 16:25:18]

Done.

+    bool run = _queue.isEmpty;
+    _queue.addLast(callback);
+    if (run) {
+      new Timer(const Duration(), () {

[floitsch, 2013/02/25 16:07:13]

Duration(milliseconds: 0)

[Anders Johnsen, 2013/02/25 16:25:18]

Done.

+        var queue = _queue;

[floitsch, 2013/02/25 16:07:13]

Use type.

[Anders Johnsen, 2013/02/25 16:25:18]

Done.

+        _queue = new Queue();

[Søren Gjesse, 2013/02/25 16:00:38]

Please make a comment to why you create a new queue here (not starving real
timers I presume).

[Anders Johnsen, 2013/02/25 16:25:18]

Done.

+        while (!queue.isEmpty) {

[floitsch, 2013/02/25 16:07:13]

With the list:
function runQueued(List queued, int startAt) {
  for (int i = startAt; i < queued.length; i++) {
    Function f = queued[i];
    try {
      f();
    } catch(e) {
      _list.insertRange(0, 1);
      _list[0] = () => runQueued(queued, i + 1);
      throw;  // rethrow.
    }
  }
}
List queued = _list;
_list = new List<Function>();
runQueued(queued, 0);

[Anders Johnsen, 2013/02/25 16:25:18]

Didn't do exactly this, but close.

+          // Let it fall-through, as we already are at the top of the stack.
+          queue.removeFirst()();
+        }
+      });
+    }
   }
 
   /**