Reland of Change extension icon load errors to warnings

extensions/utility/unpacker.cc

Index: extensions/utility/unpacker.cc
diff --git a/extensions/utility/unpacker.cc b/extensions/utility/unpacker.cc
index c230f8273bb9355ac2dd9584702367d7f784ed0f..be0a4b53eb2742f5e3a74e72c937a97bd55a8939 100644
--- a/extensions/utility/unpacker.cc
+++ b/extensions/utility/unpacker.cc
@@ -187,9 +187,8 @@
   // Decode any images that the browser needs to display.
   std::set<base::FilePath> image_paths =
       ExtensionsClient::Get()->GetBrowserImagePaths(extension.get());
-  for (std::set<base::FilePath>::iterator it = image_paths.begin();
-       it != image_paths.end(); ++it) {
-    if (!AddDecodedImage(*it))
+  for (const base::FilePath& path : image_paths) {
+    if (!AddDecodedImage(path))
       return false;  // Error was already reported.
   }