Add public deps to GN

tools/gn/deps_iterator.cc

Index: tools/gn/deps_iterator.cc
diff --git a/tools/gn/deps_iterator.cc b/tools/gn/deps_iterator.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1f964f38461af15f1caf71dfada67cb4d42158bc
--- /dev/null
+++ b/tools/gn/deps_iterator.cc
@@ -0,0 +1,48 @@
+// 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/deps_iterator.h"
+
+#include "tools/gn/target.h"
+
+DepsIterator::DepsIterator(const Target* t) : current_index_(0) {
+  vect_stack_[0] = &t->public_deps();
+  vect_stack_[1] = &t->private_deps();
+  vect_stack_[2] = &t->data_deps();
+
+  if (vect_stack_[0]->empty())
+    Advance();
+}
+
+// Iterate over the public and private linked deps, but not the data deps.
+DepsIterator::DepsIterator(const Target* t, LinkedOnly) : current_index_(0) {
+  vect_stack_[0] = &t->public_deps();
+  vect_stack_[1] = &t->private_deps();
+  vect_stack_[2] = NULL;
+
+  if (vect_stack_[0]->empty())
+    Advance();
+}
+
+// Advance to the next position. This assumes there are more vectors.
+//
+// For internal use, this function tolerates an initial index equal to the
+// length of the current vector. In this case, it will advance to the next
+// one.
+void DepsIterator::Advance() {
+  DCHECK(vect_stack_[0]);
+
+  current_index_++;
+  if (current_index_ >= vect_stack_[0]->size()) {
+    // Advance to next vect. Shift the elements left by one.
+    vect_stack_[0] = vect_stack_[1];
+    vect_stack_[1] = vect_stack_[2];
+    vect_stack_[2] = NULL;
+
+    current_index_ = 0;
+
+    if (vect_stack_[0] && vect_stack_[0]->empty())
+      Advance();
+  }
+}