tools/gn: Convert for loops to use the new range-based loops in C++11.

tools/gn/ninja_copy_target_writer.cc

 // 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 "tools/gn/ninja_copy_target_writer.h"
 
 #include "base/strings/string_util.h"
 #include "tools/gn/ninja_utils.h"
 #include "tools/gn/output_file.h"
 #include "tools/gn/scheduler.h"
@@ skipping 82 matching lines @@
   // dependency will be fine as long as the input to the copy is properly
   // listed as the output from the step that generated it.
   //
   // Moreover, doing this assumes that the copy step is always a simple
   // locally run command, so there is no need for a toolchain dependency.
   //
   // Note that there is the need in some cases for order-only dependencies
   // where a command might need to make sure something else runs before it runs
   // to avoid conflicts. Such cases should be avoided where possible, but
   // sometimes that's not possible.
-  for (size_t i = 0; i < target_->sources().size(); i++) {
-    const SourceFile& input_file = target_->sources()[i];
-
+  for (const auto& input_file : target_->sources()) {
     OutputFile output_file =
         SubstitutionWriter::ApplyPatternToSourceAsOutputFile(
             target_->settings(), output_subst, input_file);
     output_files->push_back(output_file);
 
     out_ << "build ";
     path_output_.WriteFile(out_, output_file);
     out_ << ": " << tool_name << " ";
     path_output_.WriteFile(out_, input_file);
     if (!input_dep.value().empty()) {
       out_ << " || ";
       path_output_.WriteFile(out_, input_dep);
     }
     out_ << std::endl;
   }
 }