Factor out checkerboard function in gm and sampleapp into tools.

gm/imagefiltersclipped.cpp

Index: gm/imagefiltersclipped.cpp
diff --git a/gm/imagefiltersclipped.cpp b/gm/imagefiltersclipped.cpp
index beb2e0977a6f1a7f4512179539a05cf683bff315..259342cc277cae6f0aaa2a7e7c71adb78eaa2eab 100644
--- a/gm/imagefiltersclipped.cpp
+++ b/gm/imagefiltersclipped.cpp
@@ -5,19 +5,20 @@
  * found in the LICENSE file.
  */
 
-#include "gm.h"
-#include "SkColor.h"
+#include "Checkerboard.h"
 #include "SkBitmapSource.h"
 #include "SkBlurImageFilter.h"
+#include "SkColor.h"
 #include "SkDisplacementMapEffect.h"
 #include "SkDropShadowImageFilter.h"
 #include "SkGradientShader.h"
+#include "SkMatrixImageFilter.h"
 #include "SkMorphologyImageFilter.h"
 #include "SkOffsetImageFilter.h"
 #include "SkPerlinNoiseShader.h"
 #include "SkRectShaderImageFilter.h"
-#include "SkMatrixImageFilter.h"
 #include "SkScalar.h"
+#include "gm.h"
 
 #define RESIZE_FACTOR_X SkIntToScalar(2)
 #define RESIZE_FACTOR_Y SkIntToScalar(5)
@@ -40,27 +41,6 @@ protected:
         return SkISize::Make(860, 500);
     }
 
-    void make_checkerboard() {
-        fCheckerboard.allocN32Pixels(64, 64);
-        SkCanvas canvas(fCheckerboard);
-        canvas.clear(0x00000000);
-        SkPaint darkPaint;
-        darkPaint.setColor(0xFF404040);
-        SkPaint lightPaint;
-        lightPaint.setColor(0xFFA0A0A0);
-        for (int y = 0; y < 64; y += 16) {
-          for (int x = 0; x < 64; x += 16) {
-            canvas.save();
-            canvas.translate(SkIntToScalar(x), SkIntToScalar(y));
-            canvas.drawRect(SkRect::MakeXYWH(0, 0, 8, 8), darkPaint);
-            canvas.drawRect(SkRect::MakeXYWH(8, 0, 8, 8), lightPaint);
-            canvas.drawRect(SkRect::MakeXYWH(0, 8, 8, 8), lightPaint);
-            canvas.drawRect(SkRect::MakeXYWH(8, 8, 8, 8), darkPaint);
-            canvas.restore();
-          }
-        }
-    }
-
     void make_gradient_circle(int width, int height) {
         SkScalar x = SkIntToScalar(width / 2);
         SkScalar y = SkIntToScalar(height / 2);
@@ -82,7 +62,10 @@ protected:
 
     void onDraw(SkCanvas* canvas) SK_OVERRIDE {
         if (!fInitialized) {
-            this->make_checkerboard();
+            fCheckerboard.allocN32Pixels(64, 64);
+            SkCanvas checkerboardCanvas(fCheckerboard);
+            sk_tools::DrawCheckerboard(&checkerboardCanvas, 0xFFA0A0A0, 0xFF404040, 8);
+
             this->make_gradient_circle(64, 64);
             fInitialized = true;
         }