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

chrome/browser/icon_loader_auralinux.cc

Index: chrome/browser/icon_loader_auralinux.cc
diff --git a/chrome/browser/icon_loader_auralinux.cc b/chrome/browser/icon_loader_auralinux.cc
index df7b1ee08a6b140cfbcb07e6e2fd8128d2f9310a..1d125807d7896d919f986be117840efebd89847b 100644
--- a/chrome/browser/icon_loader_auralinux.cc
+++ b/chrome/browser/icon_loader_auralinux.cc
@@ -15,10 +15,18 @@ IconGroupID IconLoader::ReadGroupIDFromFilepath(
   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_) {