Migrate HidServiceLinux and HidConnectionLinux to BrowserThread::UI.

extensions/browser/api/hid/hid_device_manager.cc

Index: extensions/browser/api/hid/hid_device_manager.cc
diff --git a/extensions/browser/api/hid/hid_device_manager.cc b/extensions/browser/api/hid/hid_device_manager.cc
index 838099ef8d284d5f53b1e68d6a69391839535345..1490e87303bb66111f5e4ec04faab6b701f4b96c 100644
--- a/extensions/browser/api/hid/hid_device_manager.cc
+++ b/extensions/browser/api/hid/hid_device_manager.cc
@@ -148,12 +148,11 @@ bool HidDeviceManager::HasPermission(const Extension* extension,
 
 // static
 bool HidDeviceManager::IsCalledOnValidThread() {
-#if defined(OS_MACOSX)
-  // Migration from FILE thread to UI thread. OS X gets it first.
-  return content::BrowserThread::CurrentlyOn(content::BrowserThread::UI);
-#else
-  // TODO(reillyg): Migrate Linux/CrOS and Windows as well.
+#if defined(OS_WIN)
+  // TODO(reillyg): Migrate Windows backend from FILE thread to UI thread.
   return content::BrowserThread::CurrentlyOn(content::BrowserThread::FILE);
+#else
+  return content::BrowserThread::CurrentlyOn(content::BrowserThread::UI);
 #endif
 }