Add 1.5x dimens for screens that are large enough

For phones with smallest width at least 480 dp, we can scale
everything by 1.5x to fill in the space better. For phones with less
width than this, we maintain the current 320 dp specification.

Bug: 131610834
Test: Emulate on 240x320 ldpi, 480x800 hdpi, 480x800 mdpi, 800x1280 mdpi
on both portrait and landscape and layouts work as intended
Change-Id: I3f7d28dc22aa3a2de96b3de51b1aa5b5c2cb19fc

go/quickstep/res/values-sw480dp/dimens.xml

@@ -0,0 +1,30 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+     Copyright (C) 2019 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.
+-->
+<resources>
+    <dimen name="recents_list_width">480dp</dimen>
+
+    <dimen name="task_item_height">90dp</dimen>
+    <dimen name="task_item_top_margin">16dp</dimen>
+    <dimen name="task_thumbnail_icon_horiz_margin">20dp</dimen>
+
+    <dimen name="task_thumbnail_corner_radius">4dp</dimen>
+
+    <dimen name="clear_all_item_view_height">48dp</dimen>
+    <dimen name="clear_all_item_view_top_margin">28dp</dimen>
+    <dimen name="clear_all_item_view_landscape_bottom_margin">28dp</dimen>
+    <dimen name="clear_all_button_width">140dp</dimen>
+</resources>