Pass a TaskRunner through ViewsDelegate to put AX init on FILE thread

chrome/browser/ui/views/chrome_views_delegate.h

Index: chrome/browser/ui/views/chrome_views_delegate.h
diff --git a/chrome/browser/ui/views/chrome_views_delegate.h b/chrome/browser/ui/views/chrome_views_delegate.h
index d4d197f127122bb8efab8ac832dbf9f31c3934ec..3c03970bc2dae415d69063ff3e1536325ccfcdd2 100644
--- a/chrome/browser/ui/views/chrome_views_delegate.h
+++ b/chrome/browser/ui/views/chrome_views_delegate.h
@@ -49,6 +49,7 @@ class ChromeViewsDelegate : public views::ViewsDelegate {
 #endif
   ui::ContextFactory* GetContextFactory() override;
   std::string GetApplicationName() override;
+  scoped_refptr<base::TaskRunner> GetInitializationTaskRunner() override;

[sky, 2015/04/24 20:52:28]

GetInitializationTaskRunner is very generic. The task-runner that is returned
likely depends on exactly what the task-runner is going to be used for. I'm
inclined to name this more specifically right now. If we need more we name it
more generically and add an enum. I'm specifically thinking of something like: 
GetTaskRunnerForAccessibilityInitialization.

[dmazzoni, 2015/04/24 21:23:43]

OK, if we want to be really specific, we should specify this is only for Aura
Linux; there's nothing blocking we have to do on other platforms.

Renamed GetTaskRunnerForAuraLinuxAccessibilityInit and ifdefed it to only that
build.

 #if defined(OS_WIN)
   virtual int GetAppbarAutohideEdges(HMONITOR monitor,
                                      const base::Closure& callback) override;