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

chrome/browser/icon_loader_auralinux.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/icon_loader.h"
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/nix/mime_util_xdg.h"
 #include "ui/views/linux_ui/linux_ui.h"
 
 // static
 IconGroupID IconLoader::ReadGroupIDFromFilepath(
     const base::FilePath& filepath) {
   return base::nix::GetFileMimeType(filepath);
 }
 
+// static
 bool IconLoader::IsIconMutableFromFilepath(const base::FilePath&) {
   return false;
 }
 
+// static
+content::BrowserThread::ID IconLoader::ReadIconThreadID() {
+  // ReadIcon() calls into views::LinuxUI and GTK2 code, so it must be on the UI
+  // thread.
+  return content::BrowserThread::UI;
+}
+
 void IconLoader::ReadIcon() {
   int size_pixels = 0;
   switch (icon_size_) {
     case IconLoader::SMALL:
       size_pixels = 16;
       break;
     case IconLoader::NORMAL:
       size_pixels = 32;
       break;
     case IconLoader::LARGE:
       size_pixels = 48;
       break;
     default:
       NOTREACHED();
   }
 
   views::LinuxUI* ui = views::LinuxUI::instance();
   if (ui) {
     gfx::Image image = ui->GetIconForContentType(group_, size_pixels);
     if (!image.IsEmpty())
       image_.reset(new gfx::Image(image));
   }
 
   target_message_loop_->PostTask(
       FROM_HERE, base::Bind(&IconLoader::NotifyDelegate, this));
 }