Add support for Low Priorirty tasks.

Source/platform/exported/WebSchedulerProxy.cpp

Index: Source/platform/exported/WebSchedulerProxy.cpp
diff --git a/Source/platform/exported/WebSchedulerProxy.cpp b/Source/platform/exported/WebSchedulerProxy.cpp
index 016abb0248d2e33a302623af6ab3312e2b3520cb..172733cf8d4674e5f45a0d27c33ded96dbc7bf52 100644
--- a/Source/platform/exported/WebSchedulerProxy.cpp
+++ b/Source/platform/exported/WebSchedulerProxy.cpp
@@ -49,4 +49,10 @@ void WebSchedulerProxy::postCompositorTask(const WebTraceLocation& webLocation,
     m_scheduler->postCompositorTask(location, bind(&runTask, adoptPtr(task)));
 }
 
+void WebSchedulerProxy::postIpcTask(const WebTraceLocation& webLocation, WebThread::Task* task)
+{
+    TraceLocation location(webLocation.functionName(), webLocation.fileName());
+    m_scheduler->postIpcTask(location, bind(&runTask, adoptPtr(task)));
+}
+
 } // namespace blink