Use Runtime.gc instead of System.gc for DDMS.

System.gc doesn't always do a GC unless to attempt to run the
finalizers after you call System.gc.

Bug: 14325353
Change-Id: Iebed7fad5576d610cea13a86e7d3d46652c67478

core/java/android/ddm/DdmHandleHeap.java

@@ -219,7 +219,7 @@ public class DdmHandleHeap extends ChunkHandler {
 
         if (false)
             Log.d("ddm-heap", "Heap GC request");
-        System.gc();
+        Runtime.getRuntime().gc();
 
         return null;        // empty response
     }