Avoid using declarations in headers which introduce symbol conflicts.

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

Index: third_party/WebKit/Source/core/inspector/InspectorWorkerAgent.h
diff --git a/third_party/WebKit/Source/core/inspector/InspectorWorkerAgent.h b/third_party/WebKit/Source/core/inspector/InspectorWorkerAgent.h
index 103350358618f3665062b19b22b75da49e4fc866..9666fbe36a037dbc1b2293fa36a901ab5241d339 100644
--- a/third_party/WebKit/Source/core/inspector/InspectorWorkerAgent.h
+++ b/third_party/WebKit/Source/core/inspector/InspectorWorkerAgent.h
@@ -52,7 +52,7 @@ class CORE_EXPORT InspectorWorkerAgent final
   ~InspectorWorkerAgent() override;
   DECLARE_VIRTUAL_TRACE();
 
-  Response disable() override;
+  protocol::Response disable() override;
   void restore() override;
   void didCommitLoadForLocalFrame(LocalFrame*) override;
 
@@ -62,9 +62,10 @@ class CORE_EXPORT InspectorWorkerAgent final
   void workerTerminated(WorkerInspectorProxy*);
 
   // Called from Dispatcher
-  Response setAutoAttach(bool autoAttach, bool waitForDebuggerOnStart) override;
-  Response sendMessageToTarget(const String& targetId,
-                               const String& message) override;
+  protocol::Response setAutoAttach(bool autoAttach,
+                                   bool waitForDebuggerOnStart) override;
+  protocol::Response sendMessageToTarget(const String& targetId,
+                                         const String& message) override;
 
   void setTracingSessionId(const String&);