Added FloatingAppBarScrollingViewBehavior

-Added FloatingAppBarScrollingViewBehavior for search bar. It can be scolling,
 transparent and overlapped the scrolling child view.
-Exchanged the position of NestedScrollView and AppBarLayout in
 settings_homepage_container.xml.
-Set the app bar height.

Change-Id: I6ef4c9001a1f893292fcbc825a0a9f2069b7286b
Fixes: 118886724
Test: robotest

tests/robotests/src/com/android/settings/widget/FloatingAppBarScrollingViewBehaviorTest.java

@@ -0,0 +1,63 @@
+/*
+ * 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.widget;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import android.content.Context;
+import android.graphics.Color;
+import android.graphics.drawable.ColorDrawable;
+
+import com.android.settings.R;
+import com.android.settings.testutils.SettingsRobolectricTestRunner;
+
+import com.google.android.material.appbar.AppBarLayout;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.Robolectric;
+import org.robolectric.RuntimeEnvironment;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+public class FloatingAppBarScrollingViewBehaviorTest {
+
+    private FloatingAppBarScrollingViewBehavior mScrollingViewBehavior;
+    private Context mContext;
+
+    @Before
+    public void setUp() {
+        mContext = RuntimeEnvironment.application;
+        mScrollingViewBehavior = new FloatingAppBarScrollingViewBehavior(mContext,
+                Robolectric.buildAttributeSet().build());
+    }
+
+    @Test
+    public void shouldHeaderOverlapScrollingChild_returnTrue() {
+        assertThat(mScrollingViewBehavior.shouldHeaderOverlapScrollingChild()).isTrue();
+    }
+
+    @Test
+    public void setAppBarLayoutTransparent_backgroundDefaultAsWhite_shouldBeTransparent() {
+        mContext.setTheme(R.style.Theme_Settings_Home);
+        final AppBarLayout appBarLayout = new AppBarLayout(mContext);
+        appBarLayout.setBackgroundColor(Color.WHITE);
+        mScrollingViewBehavior.setAppBarLayoutTransparent(appBarLayout);
+        assertThat(((ColorDrawable) appBarLayout.getBackground()).getColor()).isEqualTo(
+                Color.TRANSPARENT);
+    }
+}