runEOM

We only have one mechanism left that explicitly needs to wait to EOM to run which is responding to assignment to template.model.

This private API will be used by TemplateBinding, and allow the removal of the more complex and expensive ensureScheduled.

R=arv
BUG=

Review URL: https://codereview.appspot.com/48100043

src/observe.js

@@ -343,6 +343,41 @@
     };
   }
 
+  var eomTasks = [];
+  function runEOMTasks() {
+    if (!eomTasks.length)
+      return false;
+
+    for (var i = 0; i < eomTasks.length; i++) {
+      eomTasks[i]();
+    }
+    eomTasks.length = 0;
+    return true;
+  }
+
+  var runEOM = hasObserve ? (function(){
+    var eomObj = { pingPong: true };
+    var eomRunScheduled = false;
+
+    Object.observe(eomObj, function() {
+      runEOMTasks();
+      eomRunScheduled = false;
+    });
+
+    return function(fn) {
+      eomTasks.push(fn);
+      if (!eomRunScheduled) {
+        eomRunScheduled = true;
+        eomObj.pingPong = !eomObj.pingPong;
+      }
+    };
+  })() :
+  (function() {
+    return function(fn) {
+      eomTasks.push(fn);
+    };
+  })();
+
   var observedObjectCache = [];
 
   function newObservedObject() {
@@ -589,6 +624,8 @@
 
         allObservers.push(observer);
       }
+      if (runEOMTasks())
+        anyChanged = true;
     } while (cycles < MAX_DIRTY_CHECK_CYCLES && anyChanged);
 
     if (global.testingExposeCycleCount)
@@ -1456,6 +1493,7 @@
   }
 
   global.Observer = Observer;
+  global.Observer.runEOM_ = runEOM;
   global.Observer.hasObjectObserve = hasObserve;
   global.ArrayObserver = ArrayObserver;
   global.ArrayObserver.calculateSplices = function(current, previous) {