content_gl_tests should skip RGB565 test if the prior detection of format support fails.

content/browser/renderer_host/render_widget_host_view_mac.mm

Index: content/browser/renderer_host/render_widget_host_view_mac.mm
diff --git a/content/browser/renderer_host/render_widget_host_view_mac.mm b/content/browser/renderer_host/render_widget_host_view_mac.mm
index 5a4e688cae6fd6e9d855baea750b5c1765f568c3..3b68caf048017dbeaa47060de9dec4bde6747114 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac.mm
@@ -1134,7 +1134,12 @@ BackingStore* RenderWidgetHostViewMac::AllocBackingStore(
 void RenderWidgetHostViewMac::CopyFromCompositingSurface(
     const gfx::Rect& src_subrect,
     const gfx::Size& dst_size,
-    const base::Callback<void(bool, const SkBitmap&)>& callback) {
+    const base::Callback<void(bool, const SkBitmap&)>& callback,
+    bool readback_config_rgb565) {
+  if (readback_config_rgb565) {
+    NOTIMPLEMENTED();
+    callback.Run(false, SkBitmap());
+  }
   base::ScopedClosureRunner scoped_callback_runner(
       base::Bind(callback, false, SkBitmap()));
   float scale = ScaleFactor(cocoa_view_);