[DevTools] Support multiple sessions in content/ domain handlers

content/browser/devtools/devtools_io_context.h

Index: content/browser/devtools/devtools_io_context.h
diff --git a/content/browser/devtools/devtools_io_context.h b/content/browser/devtools/devtools_io_context.h
index 92f72b45df7e5108d6c4490fb92d29c45dd522f7..2bacfb2b7353ce2a441d3458c49cb297b052be0b 100644
--- a/content/browser/devtools/devtools_io_context.h
+++ b/content/browser/devtools/devtools_io_context.h
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#ifndef CONTENT_BROWSER_DEVTOOLS_DEVTOOLS_IO_CONTEXT_H_
+#define CONTENT_BROWSER_DEVTOOLS_DEVTOOLS_IO_CONTEXT_H_
+
 #include <stddef.h>
 
 #include <map>
@@ -61,3 +64,5 @@ class DevToolsIOContext {
 };
 
 }  // namespace content
+
+#endif  // CONTENT_BROWSER_DEVTOOLS_DEVTOOLS_IO_CONTEXT_H_