Add a generic blue background on some homepage tiles

If a homepage tile is injected from external packages, we can't
control what their icons look like, so we put a generic blue circular
background to make it consistent with the other icons.

Change-Id: I2a935db37fff097ae15540262bff94efea55179a
Fixes: 69314641
Test: robotests

src/com/android/settings/dashboard/RoundedHomepageIcon.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.settings.dashboard;
+
+import android.content.Context;
+import android.graphics.drawable.Drawable;
+import android.graphics.drawable.LayerDrawable;
+
+import com.android.settings.R;
+
+public class RoundedHomepageIcon extends LayerDrawable {
+
+    public RoundedHomepageIcon(Context context, Drawable foreground) {
+        super(new Drawable[] {
+                context.getDrawable(R.drawable.ic_homepage_generic_background),
+                foreground
+        });
+        final int insetPx = context.getResources()
+                .getDimensionPixelSize(R.dimen.dashboard_tile_foreground_image_inset);
+        setLayerInset(1 /* index */, insetPx, insetPx, insetPx, insetPx);
+    }
+}