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

chrome/browser/icon_loader_linux.cc

 // Copyright (c) 2012 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 <string>
 
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/nix/mime_util_xdg.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/codec/png_codec.h"
 #include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/size.h"
 
 using std::string;
 
 // 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() {
+  return content::BrowserThread::FILE;

[Nico, 2014/03/11 16:26:19]

Isn't icon_loader_linux gtk too? Why would linux/aura need this but linux/gtk
wouldn't?

[davidben, 2014/03/11 16:37:13]

It's a little bizarre since linux/aura is more native than linux/gtk in this
regard.

The GTK port uses our own implementation of this, but it didn't actually work
(http://crbug.com/102211). I fixed it for Aura by having it just use the GTK
native implementation (which was too crashy originally or something?) and didn't
bother duplicating it for the GTK port. They aren't really arranged to easily be
able to share GTK code. That both fixed the problem and lets us remove our
reimplemented icon theme logic when the GTK port goes away...

...except that it introduced this threading problem.

+}
+
 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:
@@ skipping 24 matching lines @@
       image_.reset(new gfx::Image(image_skia));
     } else {
       LOG(WARNING) << "Unsupported file type or load error: "
                    << filename.value();
     }
   }
 
   target_message_loop_->PostTask(
       FROM_HERE, base::Bind(&IconLoader::NotifyDelegate, this));
 }