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

Source/core/inspector/InspectorBaseAgent.cpp

Index: Source/core/inspector/InspectorBaseAgent.cpp
diff --git a/Source/core/inspector/InspectorBaseAgent.cpp b/Source/core/inspector/InspectorBaseAgent.cpp
index 5d93086ddf14d1583ebadeecd0cbc6efc1bd94ac..e1b4e8abba2be36bf385cb664eba49da646358b2 100644
--- a/Source/core/inspector/InspectorBaseAgent.cpp
+++ b/Source/core/inspector/InspectorBaseAgent.cpp
@@ -94,5 +94,11 @@ void InspectorAgentRegistry::discardAgents()
         m_agents[i]->discardAgent();
 }
 
+void InspectorAgentRegistry::flushPendingFrontendMessages()
+{
+    for (size_t i = 0; i < m_agents.size(); i++)
+        m_agents[i]->flushPendingFrontendMessages();
+}
+
 } // namespace WebCore