Remove VM-locking yield mode per discussion

src/engine/sequencer.js

@@ -32,13 +32,6 @@ Sequencer.WORK_TIME = 10;
 Sequencer.prototype.stepThreads = function (threads) {
     // Start counting toward WORK_TIME
     this.timer.start();
-    // Check for a blocking thread.
-    var blockingThread = this.getBlockingThread_(threads);
-    if (blockingThread) {
-        // Attempt to resolve any timeouts, but otherwise stop stepping.
-        blockingThread.resolveTimeouts();
-        return [];
-    }
     // List of threads which have been killed by this step.
     var inactiveThreads = [];
     // If all of the threads are yielding, we should yield.
@@ -70,10 +63,6 @@ Sequencer.prototype.stepThreads = function (threads) {
                 activeThread.status = Thread.STATUS_RUNNING;
                 // @todo Deal with the return value
             }
-            // Has the thread gone into "blocking" mode? If so, stop stepping.
-            if (activeThread.status === Thread.STATUS_YIELD_BLOCK) {
-                return inactiveThreads;
-            }
             if (activeThread.stack.length === 0 &&
                 activeThread.status === Thread.STATUS_DONE) {
                 // Finished with this thread - tell runtime to clean it up.
@@ -89,20 +78,6 @@ Sequencer.prototype.stepThreads = function (threads) {
     return inactiveThreads;
 };
 
-/**
- * Return the thread blocking all other threads, if one exists.
- * @param {Array.<Thread>} threads List of which threads to check.
- * @return {?Thread} The blocking thread if one exists.
- */
-Sequencer.prototype.getBlockingThread_ = function (threads) {
-    for (var i = 0; i < threads.length; i++) {
-        if (threads[i].status === Thread.STATUS_YIELD_BLOCK) {
-            return threads[i];
-        }
-    }
-    return null;
-};
-
 /**
  * Step the requested thread
  * @param {!Thread} thread Thread object to step