DevTools: Fix non-clean debug_devtools build after r183664

Source/devtools/scripts/concatenate_application_code.py

 #!/usr/bin/env python
 #
 # 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.
 
 """
 Release:
   - Concatenates autostart modules, application modules' module.json descriptors,
     and the application loader into a single script.
@@ skipping 47 matching lines @@
         os.mkdir(dest_dir)
         for name in files:
             src_name = join(src_dir, name)
             dest_name = join(dest_dir, name)
             if hasattr(os, 'link'):
                 os.link(src_name, dest_name)
             else:
                 shutil.copy(src_name, dest_name)
 
 
+def safe_copy(src, dest):
+    if path.exists(dest):
+        os.remove(dest)
+    shutil.copy(src, dest)
+
+
 class AppBuilder:
     def __init__(self, application_name, descriptors, application_dir, output_dir):
         self.application_name = application_name
         self.descriptors = descriptors
         self.application_dir = application_dir
         self.output_dir = output_dir
 
     def app_file(self, extension):
         return self.application_name + '.' + extension
 
@@ skipping 124 matching lines @@
 # Outputs:
 #   <app_name>.html as-is
 #   <app_name>.js as-is
 #   <module_name>/<all_files>
 class DebugBuilder(AppBuilder):
     def __init__(self, application_name, descriptors, application_dir, output_dir):
         AppBuilder.__init__(self, application_name, descriptors, application_dir, output_dir)
 
     def build_app(self):
         self._build_html()
-        shutil.copy(join(self.application_dir, self.app_file('js')), self.output_dir)
+        js_name = self.app_file('js')
+        safe_copy(join(self.application_dir, js_name), join(self.output_dir, js_name))
         for module_name in self.descriptors.modules:
             module = self.descriptors.modules[module_name]
             input_module_dir = join(self.application_dir, module_name)
             output_module_dir = join(self.output_dir, module_name)
             hardlink_or_copy_dir(input_module_dir, output_module_dir)
 
     def _build_html(self):
         html_name = self.app_file('html')
-        shutil.copy(join(self.application_dir, html_name), join(self.output_dir, html_name))
+        safe_copy(join(self.application_dir, html_name), join(self.output_dir, html_name))
 
 
 def build_application(application_name, loader, application_dir, output_dir, release_mode):
     descriptors = loader.load_application(application_name + '.json')
     if release_mode:
         builder = ReleaseBuilder(application_name, descriptors, application_dir, output_dir)
     else:
         builder = DebugBuilder(application_name, descriptors, application_dir, output_dir)
     builder.build_app()