linux_aura: run IconLoader::ReadIcon on the UI thread.

chrome/browser/icon_loader_win.cc

Index: chrome/browser/icon_loader_win.cc
diff --git a/chrome/browser/icon_loader_win.cc b/chrome/browser/icon_loader_win.cc
index 09dd583ef60a692b98ec0049e83b44ef87a508a7..309c461b6e6daaa9d90fe8d9222447892fc1c164 100644
--- a/chrome/browser/icon_loader_win.cc
+++ b/chrome/browser/icon_loader_win.cc
@@ -23,12 +23,18 @@ IconGroupID IconLoader::ReadGroupIDFromFilepath(
   return filepath.value();
 }
 
+// static
 bool IconLoader::IsIconMutableFromFilepath(const base::FilePath& filepath) {
   return filepath.MatchesExtension(L".exe") ||
          filepath.MatchesExtension(L".dll") ||
          filepath.MatchesExtension(L".ico");
 }
 
+// static
+content::BrowserThread::ID IconLoader::ReadIconThreadID() {
+  return content::BrowserThread::FILE;
+}
+
 void IconLoader::ReadIcon() {
   int size = 0;
   switch (icon_size_) {