Add new preview for theme picker (Part1)

- Uses a flag to hide the new preview until it's ready.
- Uses the apply button of bottom action bar.

Screenshot:
    flag is false: https://screenshot.googleplex.com/nDyDnt708tL.png
    flag is ture: https://screenshot.googleplex.com/R76eoVL0rNy.png

Test: Manually
Bug: 146475648
Change-Id: I49e33e011da106e7773a66a1238cc462a873c1cc
diff --git a/res/layout/fragment_theme_picker.xml b/res/layout/fragment_theme_picker.xml
index d15d93f..93606ea 100644
--- a/res/layout/fragment_theme_picker.xml
+++ b/res/layout/fragment_theme_picker.xml
@@ -16,7 +16,6 @@
 -->
 <LinearLayout
     xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:app="http://schemas.android.com/apk/res-auto"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:orientation="vertical"
@@ -27,49 +26,40 @@
         android:layout_width="match_parent"
         android:layout_height="match_parent">
 
-        <androidx.constraintlayout.widget.ConstraintLayout
+        <LinearLayout
             android:id="@+id/content_section"
             android:layout_width="match_parent"
-            android:layout_height="match_parent">
+            android:layout_height="match_parent"
+            android:orientation="vertical">
 
+            <!-- The V2 preview card. -->
+            <FrameLayout
+                android:id="@+id/preview_card_container"
+                android:layout_width="match_parent"
+                android:layout_height="@dimen/preview_content_height"
+                android:paddingTop="@dimen/preview_content_padding_top"
+                android:paddingBottom="@dimen/preview_content_padding_bottom"
+                android:clipToPadding="false"
+                android:background="@color/fullscreen_preview_background"
+                android:visibility="gone">
+                <include layout="@layout/theme_preview_card_v2"/>
+            </FrameLayout>
+
+            <!-- Will remove it later. -->
             <com.android.wallpaper.widget.PreviewPager
                 android:id="@+id/theme_preview_pager"
                 android:layout_width="match_parent"
-                android:layout_height="wrap_content"
-                android:background="@color/preview_pager_background"
-                app:layout_constrainedHeight="true"
-                app:layout_constraintBottom_toTopOf="@id/options_container"
-                app:layout_constraintEnd_toEndOf="parent"
-                app:layout_constraintHeight_max="@dimen/preview_pager_max_height"
-                app:layout_constraintStart_toStartOf="parent"
-                app:layout_constraintTop_toTopOf="parent"
-                app:layout_constraintVertical_bias="0.0"
-                app:layout_constraintVertical_chainStyle="spread_inside"/>
+                android:layout_height="@dimen/preview_content_height"
+                android:background="@color/preview_pager_background"/>
 
             <androidx.recyclerview.widget.RecyclerView
                 android:id="@+id/options_container"
                 android:layout_width="match_parent"
-                android:layout_height="@dimen/options_container_height"
+                android:layout_height="0dp"
                 android:layout_gravity="bottom|center_horizontal"
                 android:layout_marginTop="10dp"
-                android:layout_weight="1"
-                app:layout_constraintEnd_toEndOf="parent"
-                app:layout_constraintStart_toStartOf="parent"
-                app:layout_constraintTop_toBottomOf="@+id/theme_preview_pager"
-                app:layout_constraintVertical_bias="1.0"/>
-
-            <Button
-                android:id="@+id/apply_button"
-                style="@style/ActionPrimaryButton"
-                android:layout_width="wrap_content"
-                android:layout_height="wrap_content"
-                android:layout_gravity="end"
-                android:layout_marginEnd="10dp"
-                android:layout_marginBottom="10dp"
-                android:text="@string/apply_theme_btn"
-                app:layout_constraintBottom_toBottomOf="parent"
-                app:layout_constraintEnd_toEndOf="parent"/>
-        </androidx.constraintlayout.widget.ConstraintLayout>
+                android:layout_weight="1"/>
+        </LinearLayout>
 
         <androidx.core.widget.ContentLoadingProgressBar
             android:id="@+id/loading_indicator"