Check system-include dependencies in GN

tools/gn/c_include_iterator_unittest.cc

 // Copyright 2014 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.
 
 #include <stddef.h>
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/c_include_iterator.h"
 #include "tools/gn/input_file.h"
 #include "tools/gn/location.h"
@@ skipping 31 matching lines @@
 
   CIncludeIterator iter(&file);
 
   base::StringPiece contents;
   LocationRange range;
   EXPECT_TRUE(iter.GetNextIncludeString(&contents, &range));
   EXPECT_EQ("foo/bar.h", contents);
   EXPECT_TRUE(RangeIs(range, 3, 11, 20)) << range.begin().Describe(true);
 
   EXPECT_TRUE(iter.GetNextIncludeString(&contents, &range));
+  EXPECT_EQ("stdio.h", contents);
+  EXPECT_TRUE(RangeIs(range, 5, 11, 18)) << range.begin().Describe(true);
+
+  EXPECT_TRUE(iter.GetNextIncludeString(&contents, &range));
   EXPECT_EQ("foo/baz.h", contents);
   EXPECT_TRUE(RangeIs(range, 7, 12, 21)) << range.begin().Describe(true);
 
   EXPECT_TRUE(iter.GetNextIncludeString(&contents, &range));
   EXPECT_EQ("la/deda.h", contents);
   EXPECT_TRUE(RangeIs(range, 8, 11, 20)) << range.begin().Describe(true);
 
   // The line annotated with "nogncheck" should be skipped.
 
   EXPECT_TRUE(iter.GetNextIncludeString(&contents, &range));
@@ skipping 88 matching lines @@
   InputFile file(SourceFile("//foo.cc"));
   file.SetContents(buffer);
 
   base::StringPiece contents;
   LocationRange range;
 
   CIncludeIterator iter(&file);
   EXPECT_TRUE(iter.GetNextIncludeString(&contents, &range));
   EXPECT_EQ("foo/bar.h", contents);
 }