DO NOT MERGE - 2-dimensional Recents activity.

This is a simple first version in the spirit of small, incremental CLs.
It is fully functional but the following will come in later changes:

* Split screen support
* Potential animations
* Alt-tab behavior
* Relayout on orientation changes

The new activity is only started when a specific system property is set.

Test: Tested new activity behavior on local Ryu. Added tests for layout logic.
Bug: 32101881
Merged-In: I550f6e7ea0de3937dbf80e5f0294676cfe567d47
Change-Id: I46a537646e98b312d831510e1d331948888ae5ce
diff --git a/packages/SystemUI/AndroidManifest.xml b/packages/SystemUI/AndroidManifest.xml
index a74fbf8..ba845bd 100644
--- a/packages/SystemUI/AndroidManifest.xml
+++ b/packages/SystemUI/AndroidManifest.xml
@@ -267,6 +267,22 @@
             </intent-filter>
         </activity>
 
+        <activity android:name=".recents.grid.RecentsGridActivity"
+                  android:label="@string/accessibility_desc_recent_apps"
+                  android:exported="false"
+                  android:launchMode="singleInstance"
+                  android:excludeFromRecents="true"
+                  android:stateNotNeeded="true"
+                  android:resumeWhilePausing="true"
+                  android:screenOrientation="behind"
+                  android:resizeableActivity="true"
+                  android:configChanges="orientation|screenSize|smallestScreenSize|screenLayout"
+                  android:theme="@style/RecentsTheme.Wallpaper">
+            <intent-filter>
+                <action android:name="com.android.systemui.recents.TOGGLE_RECENTS" />
+            </intent-filter>
+        </activity>
+
         <activity android:name=".recents.tv.RecentsTvActivity"
                   android:label="@string/accessibility_desc_recent_apps"
                   android:exported="false"