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 f499808580adb5ecf004d42d25621e3928eecdf7..58c76246e8daecc3862299d480d07bd6691479b6 100644
--- a/extensions/utility/unpacker.cc
+++ b/extensions/utility/unpacker.cc
@@ -184,9 +184,8 @@ bool Unpacker::Run() {
   // 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.
   }