Check system-include dependencies in GN

tools/gn/c_include_iterator.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 "tools/gn/c_include_iterator.h"
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/strings/string_util.h"
 #include "tools/gn/input_file.h"
@@ skipping 116 matching lines @@
 
 bool CIncludeIterator::GetNextIncludeString(base::StringPiece* out,
                                             LocationRange* location) {
   base::StringPiece line;
   int cur_line_number = 0;
   while (lines_since_last_include_ <= kMaxNonIncludeLines &&
          GetNextLine(&line, &cur_line_number)) {
     base::StringPiece include_contents;
     int begin_char;
     IncludeType type = ExtractInclude(line, &include_contents, &begin_char);
-    if (type == INCLUDE_USER && !HasNoCheckAnnotation(line)) {
-      // Only count user includes for now.
+    if (type != INCLUDE_NONE && !HasNoCheckAnnotation(line)) {
       *out = include_contents;
       *location = LocationRange(
           Location(input_file_,
                    cur_line_number,
                    begin_char,
                    -1 /* TODO(scottmg): Is this important? */),
           Location(input_file_,
                    cur_line_number,
                    begin_char + static_cast<int>(include_contents.size()),
                    -1 /* TODO(scottmg): Is this important? */));
@@ skipping 18 matching lines @@
   line_number_++;
 
   *line = file_.substr(begin, offset_ - begin);
   *line_number = line_number_;
 
   // If we didn't hit EOF, skip past the newline for the next one.
   if (offset_ < file_.size())
     offset_++;
   return true;
 }