Add initial prototype for the GN meta-buildsystem.

tools/gn/gn_main.cc

Index: tools/gn/gn_main.cc
diff --git a/tools/gn/gn_main.cc b/tools/gn/gn_main.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6f5b31e8299f522ae1681ebd58d99f0a78571a61
--- /dev/null
+++ b/tools/gn/gn_main.cc
@@ -0,0 +1,59 @@
+// 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.
+
+#include "base/at_exit.h"
+#include "base/command_line.h"
+#include "base/strings/utf_string_conversions.h"
+#include "tools/gn/commands.h"
+#include "tools/gn/err.h"
+#include "tools/gn/location.h"
+
+namespace {
+
+std::vector<std::string> GetArgs(const CommandLine& cmdline) {
+  CommandLine::StringVector in_args = cmdline.GetArgs();
+#if defined(OS_WIN)
+  std::vector<std::string> out_args;
+  for (size_t i = 0; i < in_args.size(); i++)
+    out_args.push_back(base::WideToUTF8(in_args[i]));
+  return out_args;
+#else
+  return in_args;
+#endif
+}
+
+}  // namespace
+
+int main(int argc, char** argv) {
+  base::AtExitManager at_exit;
+  CommandLine::Init(argc, argv);
+
+  std::vector<std::string> args = GetArgs(*CommandLine::ForCurrentProcess());
+
+  std::string command;
+  if (args.empty()) {
+    command = "gen";
+  } else {
+    command = args[0];
+    args.erase(args.begin());
+  }
+
+  int retval = 0;
+  if (command == "gen") {
+    retval = RunGenCommand(args);
+  } else if (command == "desc" || command == "wtf") {
+    retval = RunDescCommand(args);
+  } else if (command == "deps") {
+    retval = RunDepsCommand(args);
+  } else if (command == "tree") {
+    retval = RunTreeCommand(args);
+  } else {
+    Err(Location(),
+        "Command \"" + command + "\" unknown.").PrintToStdout();
+    retval = 1;
+  }
+
+  exit(retval);  // Don't free memory, it can be really slow!
+  return retval;
+}