Factor out checkerboard function in gm and sampleapp into tools.

samplecode/SampleUnpremul.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 "Checkerboard.h"
 #include "Resources.h"
 #include "SampleCode.h"
 #include "SkBlurMask.h"
 #include "SkBlurDrawLooper.h"
 #include "SkCanvas.h"
 #include "SkColorPriv.h"
 #include "SkForceLinking.h"
 #include "SkImageDecoder.h"
 #include "SkOSFile.h"
 #include "SkStream.h"
 #include "SkString.h"
 #include "SkSystemEventTypes.h"
 #include "SkTypes.h"
 #include "SkUtils.h"
 #include "SkView.h"
 
 __SK_FORCE_IMAGE_DECODER_LINKING;
 
-// Defined in SampleColorFilter.cpp
-extern SkShader* createChecker();
-
 /**
  *  Interprets c as an unpremultiplied color, and returns the
  *  premultiplied equivalent.
  */
 static SkPMColor premultiply_unpmcolor(SkPMColor c) {
     U8CPU a = SkGetPackedA32(c);
     U8CPU r = SkGetPackedR32(c);
     U8CPU g = SkGetPackedG32(c);
     U8CPU b = SkGetPackedB32(c);
     return SkPreMultiplyARGB(a, r, g, b);
@@ skipping 30 matching lines @@
                         return true;
                     default:
                         break;
                 }
             }
         }
         return this->INHERITED::onQuery(evt);
     }
 
     void onDrawBackground(SkCanvas* canvas) SK_OVERRIDE {
-        SkPaint paint;
-        SkAutoTUnref<SkShader> shader(createChecker());
-        paint.setShader(shader.get());
-        canvas->drawPaint(paint);
+        sk_tools::DrawCheckerboard(canvas, 0xFFCCCCCC, 0xFFFFFFFF, 12);
     }
 
     void onDrawContent(SkCanvas* canvas) SK_OVERRIDE {
         SkPaint paint;
         paint.setAntiAlias(true);
         paint.setTextSize(SkIntToScalar(24));
         SkAutoTUnref<SkBlurDrawLooper> looper(
             SkBlurDrawLooper::Create(SK_ColorBLUE,
                                      SkBlurMask::ConvertRadiusToSigma(SkIntToScalar(2)),
                                      0, 0));
@@ skipping 98 matching lines @@
 
     typedef SampleView INHERITED;
 };
 
 //////////////////////////////////////////////////////////////////////////////
 
 static SkView* MyFactory() {
     return new UnpremulView(GetResourcePath());
 }
 static SkViewRegister reg(MyFactory);