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

tests/DrawFilterTest.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 "SkCanvas.h"
 #include "SkDrawFilter.h"
 #include "SkSurface.h"
 #include "Test.h"
 
+namespace {
 class TestFilter : public SkDrawFilter {
 public:
     bool filter(SkPaint* p, Type) override {
         return true;
     }
 };
+}
 
 /**
  *  canvas.setDrawFilter is defined to be local to the save/restore block, such that if you
  *  do the following: save / modify-drawfilter / restore, the current drawfilter should be what
  *  it was before the save.
  */
 static void test_saverestore(skiatest::Reporter* reporter) {
     SkAutoTUnref<SkSurface> surface(SkSurface::NewRasterN32Premul(10, 10));
     SkCanvas* canvas = surface->getCanvas();
 
 
     SkAutoTUnref<TestFilter> df(SkNEW(TestFilter));
 
     REPORTER_ASSERT(reporter, NULL == canvas->getDrawFilter());
 
     canvas->save();
     canvas->setDrawFilter(df);
     REPORTER_ASSERT(reporter, NULL != canvas->getDrawFilter());
     canvas->restore();
 
     REPORTER_ASSERT(reporter, NULL == canvas->getDrawFilter());
 }
 
 DEF_TEST(DrawFilter, reporter) {
     test_saverestore(reporter);
 }