Introduce a basic Blink Scheduler

Source/platform/ThreadTimers.cpp

Index: Source/platform/ThreadTimers.cpp
diff --git a/Source/platform/ThreadTimers.cpp b/Source/platform/ThreadTimers.cpp
index fe7b273aedecd92b209ab2550235d9b5699d4fbf..3e62a0858631ec2af5ae3bcf6c5b7b729b1e91e4 100644
--- a/Source/platform/ThreadTimers.cpp
+++ b/Source/platform/ThreadTimers.cpp
@@ -27,10 +27,11 @@
 #include "config.h"
 #include "platform/ThreadTimers.h"
 
-#include "platform/SharedTimer.h"
 #include "platform/PlatformThreadData.h"
+#include "platform/SharedTimer.h"
 #include "platform/Timer.h"
 #include "platform/TraceEvent.h"
+#include "platform/scheduler/Scheduler.h"
 #include "wtf/CurrentTime.h"
 #include "wtf/MainThread.h"
 
@@ -138,7 +139,7 @@ void ThreadTimers::sharedTimerFiredInternal()
         timer.fired();
 
         // Catch the case where the timer asked timers to fire in a nested event loop, or we are over time limit.
-        if (!m_firingTimers || timeToQuit < monotonicallyIncreasingTime())
+        if (!m_firingTimers || timeToQuit < monotonicallyIncreasingTime() || (isMainThread() && Scheduler::shared()->shouldYieldForHighPriorityWork()))
             break;
     }