Add optional public header checking to GN build

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 "testing/gtest/include/gtest/gtest.h"
+#include "tools/gn/c_include_iterator.h"
+
+TEST(CIncludeIterator, Basic) {
+  std::string buffer;
+  buffer.append("// Some comment\n");
+  buffer.append("\n");
+  buffer.append("#include \"foo/bar.h\"\n");
+  buffer.append("\n");
+  buffer.append("#include <stdio.h>\n");
+  buffer.append("\n");
+  buffer.append(" #include \"foo/baz.h\"\n");  // Leading whitespace
+  buffer.append("#include \"la/deda.h\"\n");
+  buffer.append("#import \"weird_mac_import.h\"\n");
+  buffer.append("\n");
+  buffer.append("void SomeCode() {\n");
+
+  CIncludeIterator iter(buffer);
+
+  base::StringPiece contents;
+  EXPECT_TRUE(iter.GetNextIncludeString(&contents));
+  EXPECT_EQ("foo/bar.h", contents);
+  EXPECT_TRUE(iter.GetNextIncludeString(&contents));
+  EXPECT_EQ("foo/baz.h", contents);
+  EXPECT_TRUE(iter.GetNextIncludeString(&contents));
+  EXPECT_EQ("la/deda.h", contents);
+  EXPECT_TRUE(iter.GetNextIncludeString(&contents));
+  EXPECT_EQ("weird_mac_import.h", contents);
+  EXPECT_FALSE(iter.GetNextIncludeString(&contents));
+}
+
+// Tests that we don't search for includes indefinitely.
+TEST(CIncludeIterator, GiveUp) {
+  std::string buffer;
+  for (size_t i = 0; i < 1000; i++)
+    buffer.append("x\n");
+  buffer.append("#include \"foo/bar.h\"\n");
+
+  base::StringPiece contents;
+
+  CIncludeIterator iter(buffer);
+  EXPECT_FALSE(iter.GetNextIncludeString(&contents));
+  EXPECT_TRUE(contents.empty());
+}
+
+// Don't count blank lines, comments, and preprocessor when giving up.
+TEST(CIncludeIterator, DontGiveUp) {
+
+  std::string buffer;
+  for (size_t i = 0; i < 1000; i++)
+    buffer.push_back('\n');
+  for (size_t i = 0; i < 1000; i++)
+    buffer.append("// comment\n");
+  for (size_t i = 0; i < 1000; i++)
+    buffer.append("#preproc\n");
+  buffer.append("#include \"foo/bar.h\"\n");
+
+  base::StringPiece contents;
+
+  CIncludeIterator iter(buffer);
+  EXPECT_TRUE(iter.GetNextIncludeString(&contents));
+  EXPECT_EQ("foo/bar.h", contents);
+}