Remove unused paintScrollbarThumb impl.

content/shell/renderer/test_runner/test_interfaces.cc

Index: content/shell/renderer/test_runner/test_interfaces.cc
diff --git a/content/shell/renderer/test_runner/test_interfaces.cc b/content/shell/renderer/test_runner/test_interfaces.cc
index 5f62c15c81503a042fbc34ad2682626b85ffd356..7f6c964adcae4e4788ed9e625c461a6f9f794373 100644
--- a/content/shell/renderer/test_runner/test_interfaces.cc
+++ b/content/shell/renderer/test_runner/test_interfaces.cc
@@ -183,13 +183,8 @@ const std::vector<WebTestProxyBase*>& TestInterfaces::GetWindowList() {
 blink::WebThemeEngine* TestInterfaces::GetThemeEngine() {
   if (!test_runner_->UseMockTheme())
     return 0;
-#if defined(OS_MACOSX)
-  if (!theme_engine_.get())
-    theme_engine_.reset(new MockWebThemeEngineMac());
-#else
   if (!theme_engine_.get())
     theme_engine_.reset(new MockWebThemeEngine());
-#endif
   return theme_engine_.get();
 }