use anon namespace to avoid (silent) collisions between local test classes

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"
 
 /**
  * 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:
     bool filter(SkPaint* p, Type) override {
         p->setColor(SK_ColorRED);
         p->setMaskFilter(NULL);
         return true;
     }
 };
+}
 
 class DrawFilterGM : public skiagm::GM {
     SkAutoTUnref<SkMaskFilter> fBlur;
 
 protected:
     SkISize onISize() override {
         return SkISize::Make(320, 240);
     }
 
     SkString onShortName() override {
@@ skipping 22 matching lines @@
         canvas->setDrawFilter(NULL);
     }
 
 private:
     typedef GM INHERITED;
 };
 
 static skiagm::GM* MyFactory(void*) { return new DrawFilterGM; }
 static skiagm::GMRegistry reg(MyFactory);