Check |m_inspectedFrames| in InspectorNetworkAgent to avoid crashes.

third_party/WebKit/Source/core/inspector/InspectorNetworkAgent.h

Index: third_party/WebKit/Source/core/inspector/InspectorNetworkAgent.h
diff --git a/third_party/WebKit/Source/core/inspector/InspectorNetworkAgent.h b/third_party/WebKit/Source/core/inspector/InspectorNetworkAgent.h
index 1fc711cf1b987d114699a1dd02104aa2893de74c..d2c5ea7cec42f69506610e0a6055bd72fea12142 100644
--- a/third_party/WebKit/Source/core/inspector/InspectorNetworkAgent.h
+++ b/third_party/WebKit/Source/core/inspector/InspectorNetworkAgent.h
@@ -249,7 +249,9 @@ class CORE_EXPORT InspectorNetworkAgent final
                            std::unique_ptr<GetResponseBodyCallback>);
   void clearPendingRequestData();
 
+  // |m_inspectedFrames| is null when the agent is for worker global scopes.
   Member<InspectedFrames> m_inspectedFrames;
+
   String m_userAgentOverride;
   String m_hostId;
   Member<NetworkResourcesData> m_resourcesData;