Cleanup VulkanWindowContext for use on Android

tools/viewer/sk_app/android/WindowContext_android.h

Index: tools/viewer/sk_app/android/WindowContext_android.h
diff --git a/tools/viewer/sk_app/android/WindowContext_android.h b/tools/viewer/sk_app/android/WindowContext_android.h
new file mode 100644
index 0000000000000000000000000000000000000000..f0529fe44eee6356a39283e318115a4e653e7adc
--- /dev/null
+++ b/tools/viewer/sk_app/android/WindowContext_android.h
@@ -0,0 +1,21 @@
+/*
+* Copyright 2016 Google Inc.
+*
+* Use of this source code is governed by a BSD-style license that can be
+* found in the LICENSE file.
+*/
+
+#ifndef WindowContext_android_DEFINED
+#define WindowContext_android_DEFINED
+
+#include <android/native_window_jni.h>
+
+namespace sk_app {
+
+struct ContextPlatformData_android {
+    ANativeWindow* fNativeWindow;
+};
+
+}   // namespace sk_app
+
+#endif // WindowContext_android_DEFINED