Refactor TimeBase to post tasks. Workers to use real Idle tasks.

Source/core/dom/ScriptRunnerTest.cpp

Index: Source/core/dom/ScriptRunnerTest.cpp
diff --git a/Source/core/dom/ScriptRunnerTest.cpp b/Source/core/dom/ScriptRunnerTest.cpp
index 03d2a52b08aa895556f2f240842c360247e80127..50da07066b8fa198696dd5d0c7cd99c6d35589eb 100644
--- a/Source/core/dom/ScriptRunnerTest.cpp
+++ b/Source/core/dom/ScriptRunnerTest.cpp
@@ -88,6 +88,10 @@ class ScriptRunnerTest : public testing::Test {
 public:
     void SetUp() override
     {
+        Scheduler::shutdown();
+
+        m_oldPlatform = Platform::current();
+        Platform::initialize(&m_platform);
         m_document = Document::create();
         m_element = m_document->createElement("foo", ASSERT_NO_EXCEPTION);