Turn off Blink Scheduler by default.

Source/platform/scheduler/SchedulerTest.cpp

 // Copyright 2014 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.
 
 #include "config.h"
 #include "platform/scheduler/Scheduler.h"
 
+#include "platform/RuntimeEnabledFeatures.h"
 #include "platform/TestingPlatformSupport.h"
 #include "platform/TraceLocation.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebThread.h"
 
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
 #include <string>
 #include <vector>
 
@@ skipping 137 matching lines @@
     double m_sharedTimerFireInterval;
     double m_monotonicallyIncreasingTime;
 };
 
 class SchedulerTest : public testing::Test {
 public:
     SchedulerTest()
         : m_reentrantCount(0)
         , m_maxRecursion(4)
     {
+        blink::RuntimeEnabledFeatures::setBlinkSchedulerEnabled(true);
         SchedulerForTest::initializeOnMainThread();
         m_scheduler = static_cast<SchedulerForTest*>(Scheduler::shared());
     }
 
     ~SchedulerTest()
     {
         Scheduler::shutdown();
     }
 
     virtual void SetUp() override
@@ skipping 355 matching lines @@
     m_platformSupport.setMonotonicTimeForTest(1000.5);
     runPendingTasks();
 
     ASSERT_FALSE(m_scheduler->shouldYieldForHighPriorityWork());
     m_scheduler->postCompositorTask(FROM_HERE, WTF::bind(&dummyTask));
 
     EXPECT_FALSE(m_scheduler->shouldYieldForHighPriorityWork());
 }
 
 } // namespace