Add Dashing gpu effect for simple dashed lines

gm/dashing.cpp

Index: gm/dashing.cpp
diff --git a/gm/dashing.cpp b/gm/dashing.cpp
index 2f5be081597d55a940405b9c1fc5d323f1e68760..7102b44d44e837f83785c8f6ba8cf6cf31b7eaf1 100644
--- a/gm/dashing.cpp
+++ b/gm/dashing.cpp
@@ -313,10 +313,69 @@ protected:
 
 //////////////////////////////////////////////////////////////////////////////
 
+class Dashing4GM : public skiagm::GM {
+public:
+    Dashing4GM() {}
+
+protected:
+    virtual uint32_t onGetFlags() const SK_OVERRIDE {
+        return kSkipTiled_Flag;
+    }
+
+    SkString onShortName() {
+        return SkString("dashing4");
+    }
+
+    SkISize onISize() { return skiagm::make_isize(640, 730); }
+
+    virtual void onDraw(SkCanvas* canvas) {
+        static const struct {
+            int fOnInterval;
+            int fOffInterval;
+        } gData[] = {
+            { 1, 1 },
+            { 4, 2 },
+            { 0, 4 }, // test for zero length on interval
+        };
+
+        SkPaint paint;
+        paint.setStyle(SkPaint::kStroke_Style);
+
+        canvas->translate(SkIntToScalar(20), SkIntToScalar(20));
+        canvas->translate(0, SK_ScalarHalf);
+
+        for (int width = 0; width <= 2; ++width) {
+            for (size_t data = 0; data < SK_ARRAY_COUNT(gData); ++data) {
+                for (int aa = 0; aa <= 1; ++aa) {
+                    for (int cap = 0; cap <= 1; ++cap) {
+                        int w = width * width * width;
+                        paint.setAntiAlias(SkToBool(aa));
+                        paint.setStrokeWidth(SkIntToScalar(w));
+
+                        SkToBool(cap) ? paint.setStrokeCap(SkPaint::kSquare_Cap)
+                            : paint.setStrokeCap(SkPaint::kRound_Cap);
+
+                        int scale = w ? w : 1;
+
+                        drawline(canvas, gData[data].fOnInterval * scale,
+                                 gData[data].fOffInterval * scale,
+                                 paint);
+                        canvas->translate(0, SkIntToScalar(20));
+                    }
+                }
+            }
+        }
+    }
+};
+
+//////////////////////////////////////////////////////////////////////////////
+
 static skiagm::GM* F0(void*) { return new DashingGM; }
 static skiagm::GM* F1(void*) { return new Dashing2GM; }
 static skiagm::GM* F2(void*) { return new Dashing3GM; }
+static skiagm::GM* F3(void*) { return new Dashing4GM; }
 
 static skiagm::GMRegistry gR0(F0);
 static skiagm::GMRegistry gR1(F1);
 static skiagm::GMRegistry gR2(F2);
+static skiagm::GMRegistry gR3(F3);