Fix build of IPC fuzzing utils.

content/common/accessibility_messages.h

Index: content/common/accessibility_messages.h
diff --git a/content/common/accessibility_messages.h b/content/common/accessibility_messages.h
index 2be0c7768a80d5de934afb947097a35abe2a503b..22f40dda476b54e7f2943cd4d2f5c8edc55dfea6 100644
--- a/content/common/accessibility_messages.h
+++ b/content/common/accessibility_messages.h
@@ -17,6 +17,14 @@
 #include "ui/accessibility/ax_node_data.h"
 #include "ui/accessibility/ax_tree_update.h"
 
+// Singly-included section for custom types.
+#ifndef CONTENT_COMMON_ACCESSIBILITY_MESSAGES_H_
+#define CONTENT_COMMON_ACCESSIBILITY_MESSAGES_H_
+
+typedef std::map<int32, int> FrameIDMap;
+
+#endif  // CONTENT_COMMON_ACCESSIBILITY_MESSAGES_H_
+
 #undef IPC_MESSAGE_EXPORT
 #define IPC_MESSAGE_EXPORT CONTENT_EXPORT
 
@@ -51,8 +59,6 @@ IPC_STRUCT_TRAITS_BEGIN(ui::AXTreeUpdate)
   IPC_STRUCT_TRAITS_MEMBER(nodes)
 IPC_STRUCT_TRAITS_END()
 
-typedef std::map<int32, int> FrameIDMap;
-
 IPC_STRUCT_BEGIN(AccessibilityHostMsg_EventParams)
   // The tree update.
   IPC_STRUCT_MEMBER(ui::AXTreeUpdate, update)