Add SK_SUPPORT_LEGACY_DRAWFILTER guard around calls to SkCanvas::(get|set)DrawFilter.

gm/drawfilter.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
 #include "SkBlurMask.h"
 #include "SkBlurMaskFilter.h"
 #include "SkCanvas.h"
 #include "SkDrawFilter.h"
 #include "SkPaint.h"
 
+#ifdef SK_SUPPORT_LEGACY_DRAWFILTER
+
 /**
  * Initial test coverage for SkDrawFilter.
  * Draws two rectangles; if draw filters are broken, they will match.
  * If draw filters are working correctly, the first will be blue and blurred,
  * the second red and sharp.
  */
 
 namespace {
 class TestFilter : public SkDrawFilter {
 public:
@@ skipping 38 matching lines @@
         // Must unset if the DrawFilter is from the stack to avoid refcount errors!
         canvas->setDrawFilter(nullptr);
     }
 
 private:
     typedef GM INHERITED;
 };
 
 DEF_GM( return new DrawFilterGM; )
 
+#endif