Implement Settings UI for Screen zoom preference

Also cleans up unnecessary 0s and moves tint to the proper place in
relevant vector drawable XML files.

Preview layout is still WIP pending UX input, but I wanted to get this
CL in place so that we can test/demo the feature ASAP.

Bug: 22450672
Change-Id: Ic3f1500006c763df99fba2d1d16782b89d6fcae1

src/com/android/settings/display/ScreenZoomPreference.java

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2015 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.display;
+
+import android.content.Context;
+import android.content.Intent;
+import android.support.v4.content.res.TypedArrayUtils;
+import android.support.v7.preference.PreferenceGroup;
+import android.util.AttributeSet;
+
+/**
+ * Preference for changing the density of the display on which the preference
+ * is visible.
+ */
+public class ScreenZoomPreference extends PreferenceGroup {
+    public ScreenZoomPreference(Context context, AttributeSet attrs) {
+        super(context, attrs, TypedArrayUtils.getAttr(context,
+                android.support.v7.preference.R.attr.preferenceScreenStyle,
+                android.R.attr.preferenceScreenStyle));
+
+        setFragment("com.android.settings.display.ScreenZoomSettings");
+
+        final DisplayDensityUtils density = new DisplayDensityUtils(context);
+        final int defaultIndex = density.getCurrentIndex();
+        if (defaultIndex < 0) {
+            setVisible(false);
+            setEnabled(false);
+        } else {
+            final String[] entries = density.getEntries();
+            final int currentIndex = density.getCurrentIndex();
+            setSummary(entries[currentIndex]);
+        }
+    }
+
+    @Override
+    protected boolean isOnSameScreenAsChildren() {
+        return false;
+    }
+}