Avoid using declarations in headers which introduce symbol conflicts.

third_party/WebKit/Source/modules/accessibility/InspectorAccessibilityAgent.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef InspectorAccessibilityAgent_h
 #define InspectorAccessibilityAgent_h
 
 #include "core/inspector/InspectorBaseAgent.h"
 #include "core/inspector/protocol/Accessibility.h"
 #include "modules/ModulesExport.h"
@@ skipping 12 matching lines @@
     : public InspectorBaseAgent<protocol::Accessibility::Metainfo> {
   WTF_MAKE_NONCOPYABLE(InspectorAccessibilityAgent);
 
  public:
   InspectorAccessibilityAgent(Page*, InspectorDOMAgent*);
 
   // Base agent methods.
   DECLARE_VIRTUAL_TRACE();
 
   // Protocol methods.
-  Response getPartialAXTree(
+  protocol::Response getPartialAXTree(
       int domNodeId,
-      Maybe<bool> fetchRelatives,
+      protocol::Maybe<bool> fetchRelatives,
       std::unique_ptr<protocol::Array<protocol::Accessibility::AXNode>>*)
       override;
 
  private:
   std::unique_ptr<AXNode> buildObjectForIgnoredNode(
       Node* domNode,
       AXObject*,
       bool fetchRelatives,
       std::unique_ptr<protocol::Array<AXNode>>& nodes,
       AXObjectCacheImpl&) const;
@@ skipping 34 matching lines @@
                    std::unique_ptr<protocol::Array<AXNode>>& nodes,
                    AXObjectCacheImpl&) const;
 
   Member<Page> m_page;
   Member<InspectorDOMAgent> m_domAgent;
 };
 
 }  // namespace blink
 
 #endif  // InspectorAccessibilityAgent_h