Run explicit GC to clear references to bitmaps earlier.

Bug: 38258699
Test: Open Recents, dump meminfo, close Recents, wait, dump meminfo
Change-Id: Ibdcf94aee4fac9abcde64e30ae1f13cbb551fec0

packages/SystemUI/src/com/android/systemui/recents/RecentsActivity.java

@@ -514,6 +514,9 @@ public class RecentsActivity extends Activity implements ViewTreeObserver.OnPreD
             RecentsActivityLaunchState launchState = config.getLaunchState();
             launchState.reset();
         }
+
+        // Force a gc to attempt to clean up bitmap references more quickly (b/38258699)
+        Recents.getSystemServices().gc();
     }
 
     @Override

packages/SystemUI/src/com/android/systemui/recents/misc/SystemServicesProxy.java

@@ -361,6 +361,19 @@ public class SystemServicesProxy {
         return sSystemServicesProxy;
     }
 
+    /**
+     * Requests a gc() from the background thread.
+     */
+    public void gc() {
+        BackgroundThread.getHandler().post(new Runnable() {
+            @Override
+            public void run() {
+                System.gc();
+                System.runFinalization();
+            }
+        });
+    }
+
     /**
      * @return whether the provided {@param className} is blacklisted
      */