fix arcto exception handling

gm/arcto.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "gm.h"
 #include "SkParsePath.h"
 #include "SkPath.h"
@@ skipping 17 matching lines @@
     fill="none" stroke="red" stroke-width="5" />
 
 <path d="M250,400  A120,80 0 1,1 250,500"
     fill="none" stroke="green" stroke-width="5"/>
 
 <path d="M250,400  A120,80 0 1,0 250,500"
     fill="none" stroke="purple" stroke-width="5"/>
 
 <path d="M250,400  A120,80 0 0,1 250,500"
     fill="none" stroke="blue" stroke-width="5"/>
+
+<path d="M100,100  A  0, 0 0 0,1 200,200"
+    fill="none" stroke="blue" stroke-width="5" stroke-linecap="round"/>
+
+<path d="M200,100  A 80,80 0 0,1 200,100"
+    fill="none" stroke="blue" stroke-width="5" stroke-linecap="round"/>
 </svg>
  */
 
 DEF_SIMPLE_GM(arcto, canvas, 500, 600) {
     SkPaint paint;
     paint.setAntiAlias(true);
     paint.setStyle(SkPaint::kStroke_Style);
     paint.setStrokeWidth(2);
     paint.setColor(0xFF660000);
-    canvas->scale(2, 2);
+//    canvas->scale(2, 2);  // for testing on retina
     SkRect oval = SkRect::MakeXYWH(100, 100, 100, 100);
     SkPath svgArc;
 
     for (int angle = 0; angle <= 45; angle += 45) {
        for (int oHeight = 2; oHeight >= 1; --oHeight) {
             SkScalar ovalHeight = oval.height() / oHeight;
             svgArc.moveTo(oval.fLeft, oval.fTop);
             svgArc.arcTo(oval.width() / 2, ovalHeight, SkIntToScalar(angle), SkPath::kSmall_ArcSize,
                     SkPath::kCW_Direction, oval.right(), oval.bottom());
             canvas->drawPath(svgArc, paint);
@@ skipping 18 matching lines @@
         "M250,400  A120,80 0 1,1 250,500",
         "M250,400  A120,80 0 1,0 250,500",
         "M250,400  A120,80 0 0,1 250,500"
     };
     int cIndex = 0;
     for (const char* arcstr : arcstrs) {
         SkParsePath::FromSVGString(arcstr, &svgArc);
         paint.setColor(colors[cIndex++]);
         canvas->drawPath(svgArc, paint);
     }
+
+    // test that zero length arcs still draw round cap
+    paint.setStrokeCap(SkPaint::kRound_Cap);
+    SkPath path;
+    path.moveTo(100, 100);
+    path.arcTo(0, 0, 0, SkPath::kLarge_ArcSize, SkPath::kCW_Direction, 200, 200);
+    canvas->drawPath(path, paint);
+
+    path.reset();
+    path.moveTo(200, 100);
+    path.arcTo(80, 80, 0, SkPath::kLarge_ArcSize, SkPath::kCW_Direction, 200, 100);
+    canvas->drawPath(path, paint);
 }