Fix pure virtual call from destructor and turn VertBench back on



git-svn-id: http://skia.googlecode.com/svn/trunk@2556 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrDrawTarget.h b/src/gpu/GrDrawTarget.h
index 16326a9..7d311aa 100644
--- a/src/gpu/GrDrawTarget.h
+++ b/src/gpu/GrDrawTarget.h
@@ -1366,6 +1366,10 @@
 
     Caps fCaps;
 
+    // subclasses must call this in their destructors to ensure all vertex
+    // and index sources have been released (including those held by 
+    // pushGeometrySource())
+    void releaseGeometry();
 private:
     // called when setting a new vert/idx source to unref prev vb/ib
     void releasePreviousVertexSource();