Reapply 169371 "DevTools: defer styles delta calculation to until the end of the task"

Source/core/inspector/InspectorController.cpp

Index: Source/core/inspector/InspectorController.cpp
diff --git a/Source/core/inspector/InspectorController.cpp b/Source/core/inspector/InspectorController.cpp
index f3f7838c3dee42a9b19e6f149eacd583dd348069..64e6f3f2db46e7ebce6e7826c06caf1a8388a77e 100644
--- a/Source/core/inspector/InspectorController.cpp
+++ b/Source/core/inspector/InspectorController.cpp
@@ -428,6 +428,11 @@ void InspectorController::didProcessTask()
         domDebuggerAgent->didProcessTask();
 }
 
+void InspectorController::flushPendingFrontendMessages()
+{
+    m_agents.flushPendingFrontendMessages();
+}
+
 void InspectorController::didCommitLoadForMainFrame()
 {
     Vector<InspectorAgent*> agents = m_moduleAgents;