Reland of Change extension icon load errors to warnings

extensions/common/manifest_handler_helpers.h

Index: extensions/common/manifest_handler_helpers.h
diff --git a/extensions/common/manifest_handler_helpers.h b/extensions/common/manifest_handler_helpers.h
index b0249c30c96e51e91b95e770b53ee4e3d0795891..e1f901a7fa15a7decc5db2156239def84bc78c90 100644
--- a/extensions/common/manifest_handler_helpers.h
+++ b/extensions/common/manifest_handler_helpers.h
@@ -6,9 +6,11 @@
 #define EXTENSIONS_COMMON_MANIFEST_HANDLER_HELPERS_H_
 
 #include <string>
+#include <vector>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string16.h"
+#include "extensions/common/install_warning.h"
 
 class ExtensionIconSet;
 
@@ -17,6 +19,9 @@
 }
 
 namespace extensions {
+
+class Extension;
+
 namespace manifest_handler_helpers {
 
 // Strips leading slashes from the file path. Returns true iff the final path is
@@ -25,8 +30,10 @@
 
 // Loads icon paths defined in dictionary |icons_value| into ExtensionIconSet
 // |icons|. |icons_value| is a dictionary value {icon size -> icon path}.
-// Returns success. If load fails, |error| will be set.
-bool LoadIconsFromDictionary(const base::DictionaryValue* icons_value,
+// Returns success. If load fails, |error| will be set. Non-failure warnings may
+// be added to |extension|.
+bool LoadIconsFromDictionary(Extension* extension,
+                             const base::DictionaryValue* icons_value,
                              ExtensionIconSet* icons,
                              base::string16* error);