Cleanup: Remove unneeded base/file_util.h includes in content.

content/browser/tracing/trace_subscriber_stdio.h

Index: content/browser/tracing/trace_subscriber_stdio.h
===================================================================
--- content/browser/tracing/trace_subscriber_stdio.h	(revision 199525)
+++ content/browser/tracing/trace_subscriber_stdio.h	(working copy)
@@ -8,10 +8,13 @@
 #include <string>
 
 #include "base/compiler_specific.h"
-#include "base/file_util.h"
 #include "content/public/browser/trace_subscriber.h"
 #include "content/common/content_export.h"
 
+namespace base {
+class FilePath;
+}
+
 namespace content {
 
 class TraceSubscriberStdioImpl;