Add optional public header checking to GN build

tools/gn/trace.h

 // Copyright (c) 2013 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 TOOLS_GN_TRACE_H_
 #define TOOLS_GN_TRACE_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
 
 class Label;
 
 class TraceItem {
  public:
   enum Type {
     TRACE_FILE_LOAD,
     TRACE_FILE_PARSE,
     TRACE_FILE_EXECUTE,
     TRACE_FILE_WRITE,
     TRACE_SCRIPT_EXECUTE,
-    TRACE_DEFINE_TARGET
+    TRACE_DEFINE_TARGET,
+    TRACE_CHECK_HEADER,  // One file.
+    TRACE_CHECK_HEADERS,  // All files.
   };
 
   TraceItem(Type type,
             const std::string& name,
             base::PlatformThreadId thread_id);
   ~TraceItem();
 
   Type type() const { return type_; }
   const std::string& name() const { return name_; }
   base::PlatformThreadId thread_id() const { return thread_id_; }
@@ skipping 48 matching lines @@
 void AddTrace(TraceItem* item);
 
 // Returns a summary of the current traces, or the empty string if tracing is
 // not enabled.
 std::string SummarizeTraces();
 
 // Saves the current traces to the given filename in JSON format.
 void SaveTraces(const base::FilePath& file_name);
 
 #endif  // TOOLS_GN_TRACE_H_