Add MetalayerToolTest

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 5110f2661c808aa01bc61cbf5399f24362f810e4..eb529bf5bf295afe584bfc29ab2791719b92a1f6 100644
--- a/ash/test/test_palette_delegate.cc
+++ b/ash/test/test_palette_delegate.cc
@@ -45,10 +45,13 @@ void TestPaletteDelegate::TakePartialScreenshot(const base::Closure& done) {
 void TestPaletteDelegate::CancelPartialScreenshot() {}
 
 bool TestPaletteDelegate::IsMetalayerSupported() {
-  return false;
+  return is_metalayer_supported_;
 }
 
-void TestPaletteDelegate::ShowMetalayer(const base::Closure& closed) {}
+void TestPaletteDelegate::ShowMetalayer(const base::Closure& closed) {
+  ++show_metalayer_count_;
+  metalayer_closed_ = closed;
+}
 
 void TestPaletteDelegate::HideMetalayer() {}