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

chrome/browser/icon_loader.h

Index: chrome/browser/icon_loader.h
diff --git a/chrome/browser/icon_loader.h b/chrome/browser/icon_loader.h
index ef602128276df9465020585112b8a6785a44703b..0e48a45fe33a3bf798aaeff14393ac01f0e81a4a 100644
--- a/chrome/browser/icon_loader.h
+++ b/chrome/browser/icon_loader.h
@@ -14,6 +14,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop_proxy.h"
+#include "content/public/browser/browser_thread.h"
 #include "ui/gfx/image/image.h"
 
 #if defined(OS_WIN)
@@ -77,6 +78,9 @@ class IconLoader : public base::RefCountedThreadSafe<IconLoader> {
   // Some icons (exe's on windows) can change as they're loaded.
   static bool IsIconMutableFromFilepath(const base::FilePath& path);
 
+  // The thread ReadIcon() should be called on.
+  static content::BrowserThread::ID ReadIconThreadID();
+
   void ReadGroup();
   void OnReadGroup();
   void ReadIcon();