Change some more GMs to clear to opaque black, not transparent black.

gm/xfermodeimagefilter.cpp

 /*
  * Copyright 2013 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 "sk_tool_utils.h"
 #include "SkArithmeticMode.h"
@@ skipping 56 matching lines @@
 
     void onOnceBeforeDraw() override {
         make_bitmap();
 
         fCheckerboard.allocN32Pixels(80, 80);
         SkCanvas checkerboardCanvas(fCheckerboard);
         sk_tool_utils::draw_checkerboard(&checkerboardCanvas, 0xFFA0A0A0, 0xFF404040, 8);
     }
 
     void onDraw(SkCanvas* canvas) override {
-        canvas->clear(0x00000000);
+        canvas->clear(SK_ColorBLACK);
         SkPaint paint;
 
         const struct {
             SkXfermode::Mode  fMode;
             const char*         fLabel;
         } gModes[] = {
             { SkXfermode::kClear_Mode,    "Clear"     },
             { SkXfermode::kSrc_Mode,      "Src"       },
             { SkXfermode::kDst_Mode,      "Dst"       },
             { SkXfermode::kSrcOver_Mode,  "SrcOver"   },
@@ skipping 113 matching lines @@
 private:
     SkBitmap fBitmap, fCheckerboard;
     typedef GM INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 DEF_GM( return new XfermodeImageFilterGM; );
 
 }