Cleanup: Fix tools/gn header include guards.

The header include guards should match the file path from root.

These entries were found using a modified version of Eric's
fix-include-guards.py script found attached in
https://code.google.com/p/chromium/issues/detail?id=435361#c7.

BUG=435361
TEST=gn_unittests
R=scottmg@chromium.org

Review URL: https://codereview.chromium.org/968193002

Cr-Commit-Position: refs/heads/master@{#318719}

tools/gn/c_include_iterator.h

@@ -52,4 +52,4 @@ class CIncludeIterator {
   DISALLOW_COPY_AND_ASSIGN(CIncludeIterator);
 };
 
-#endif  // TOOLS_GN_INCLUDE_ITERATOR_H_
+#endif  // TOOLS_GN_C_INCLUDE_ITERATOR_H_

tools/gn/commands.h

@@ -173,4 +173,4 @@ void FilterAndPrintTargetSet(bool indent,
 
 }  // namespace commands
 
-#endif  // TOOLS_GN_COMMANDS_H
+#endif  // TOOLS_GN_COMMANDS_H_

tools/gn/ninja_build_writer.h

@@ -58,5 +58,5 @@ class NinjaBuildWriter {
   DISALLOW_COPY_AND_ASSIGN(NinjaBuildWriter);
 };
 
-#endif  // TOOLS_GN_NINJA_BUILD_GENERATOR_H_
+#endif  // TOOLS_GN_NINJA_BUILD_WRITER_H_
 

tools/gn/substitution_list.h

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef TOOLS_GN_SUBSTUTITION_LIST_H
-#define TOOLS_GN_SUBSTUTITION_LIST_H
+#ifndef TOOLS_GN_SUBSTITUTION_LIST_H_
+#define TOOLS_GN_SUBSTITUTION_LIST_H_
 
 #include <string>
 #include <vector>
@@ -43,4 +43,4 @@ class SubstitutionList {
   std::vector<SubstitutionType> required_types_;
 };
 
-#endif  // TOOLS_GN_SUBSTUTITION_LIST_H
+#endif  // TOOLS_GN_SUBSTITUTION_LIST_H_