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 36c0eba272d32a730c46936f6e1b1aaaa8411ab9..47632680bcbe05e40c8884ea3c00c3547dd819fa 100644
--- a/extensions/utility/unpacker.cc
+++ b/extensions/utility/unpacker.cc
@@ -185,9 +185,8 @@ 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.
   }