Linux: move X operations from the IO to UI2 thread.

chrome/test/testing_browser_process.h

Index: chrome/test/testing_browser_process.h
diff --git a/chrome/test/testing_browser_process.h b/chrome/test/testing_browser_process.h
index a50758663b99536f4bc43275d091dd1df83d8422..42949b0f58f4f0575d0cd848c48462edd4bc8bbd 100644
--- a/chrome/test/testing_browser_process.h
+++ b/chrome/test/testing_browser_process.h
@@ -44,6 +44,12 @@ class TestingBrowserProcess : public BrowserProcess {
     return NULL;
   }
 
+#if defined(OS_LINUX)
+  virtual base::Thread* background_x11_thread() {
+    return NULL;
+  }
+#endif
+
   virtual base::Thread* file_thread() {
     return NULL;
   }