Add default ctor to SkMask

tests/AAClipTest.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkAAClip.h"
 #include "SkCanvas.h"
 #include "SkMask.h"
@@ skipping 210 matching lines @@
     REPORTER_ASSERT(reporter, !clip0.getBounds().isEmpty());
     REPORTER_ASSERT(reporter, clip0 != clip1);
     REPORTER_ASSERT(reporter, clip0.getBounds() == r);
 
     clip0.setEmpty();
     REPORTER_ASSERT(reporter, clip0.isEmpty());
     REPORTER_ASSERT(reporter, clip0.getBounds().isEmpty());
     REPORTER_ASSERT(reporter, clip1 == clip0);
 
     SkMask mask;
-    mask.fImage = nullptr;
     clip0.copyToMask(&mask);
     REPORTER_ASSERT(reporter, nullptr == mask.fImage);
     REPORTER_ASSERT(reporter, mask.fBounds.isEmpty());
 }
 
 static void rand_irect(SkIRect* r, int N, SkRandom& rand) {
     r->setXYWH(0, 0, rand.nextU() % N, rand.nextU() % N);
     int dx = rand.nextU() % (2*N);
     int dy = rand.nextU() % (2*N);
     // use int dx,dy to make the subtract be signed
@@ skipping 197 matching lines @@
     test_empty(reporter);
     test_path_bounds(reporter);
     test_irect(reporter);
     test_rgn(reporter);
     test_path_with_hole(reporter);
     test_regressions();
     test_nearly_integral(reporter);
     test_really_a_rect(reporter);
     test_crbug_422693(reporter);
 }