Set width & height of app icons in all widgets tray to 48dp

Bug: 184877669
Test: Change the grid size and observe app icons in all widgets
      tray stay the same.
Change-Id: I856d5fada579474fffb6296d641fb686623ca2cc

res/layout/widgets_list_row_header.xml

@@ -15,6 +15,7 @@
 -->
 <com.android.launcher3.widget.picker.WidgetsListHeader xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools"
+    xmlns:launcher="http://schemas.android.com/apk/res-auto"
     android:id="@+id/widgets_list_header"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
@@ -22,7 +23,8 @@
     android:background="@drawable/widgets_list_middle_ripple"
     android:layout_marginBottom="@dimen/widget_list_entry_bottom_margin"
     android:paddingVertical="@dimen/widget_list_header_view_vertical_padding"
-    android:orientation="horizontal">
+    android:orientation="horizontal"
+    launcher:appIconSize="48dp">
 
     <ImageView
         android:id="@+id/app_icon"

src/com/android/launcher3/widget/picker/WidgetsListHeader.java

@@ -156,6 +156,11 @@ public final class WidgetsListHeader extends LinearLayout implements ItemInfoUpd
     private void applyDrawables(Drawable icon) {
         icon.setBounds(0, 0, mIconSize, mIconSize);
 
+        LinearLayout.LayoutParams layoutParams =
+                (LinearLayout.LayoutParams) mAppIcon.getLayoutParams();
+        layoutParams.width = mIconSize;
+        layoutParams.height = mIconSize;
+        mAppIcon.setLayoutParams(layoutParams);
         mAppIcon.setImageDrawable(icon);
 
         // If the current icon is a placeholder color, animate its update.