Add MetalayerMode to the palette.

ash/test/test_palette_delegate.cc

Index: ash/test/test_palette_delegate.cc
diff --git a/ash/test/test_palette_delegate.cc b/ash/test/test_palette_delegate.cc
index 49881d30e62c4b8c9053cdfd1948d1bd591eb04d..5110f2661c808aa01bc61cbf5399f24362f810e4 100644
--- a/ash/test/test_palette_delegate.cc
+++ b/ash/test/test_palette_delegate.cc
@@ -44,4 +44,12 @@ void TestPaletteDelegate::TakePartialScreenshot(const base::Closure& done) {
 
 void TestPaletteDelegate::CancelPartialScreenshot() {}
 
+bool TestPaletteDelegate::IsMetalayerSupported() {
+  return false;
+}
+
+void TestPaletteDelegate::ShowMetalayer(const base::Closure& closed) {}
+
+void TestPaletteDelegate::HideMetalayer() {}
+
 }  // namespace ash