Respecify SkCanvas::drawArc, consolidate conversion to SkPath, add GM for oddball drawArcs

src/core/SkCanvas.cpp

Index: src/core/SkCanvas.cpp
diff --git a/src/core/SkCanvas.cpp b/src/core/SkCanvas.cpp
index 0b14368b6eb98e0d5f97dc3e1dbd1fbe51035606..8f9a576761afd4ffeb8181dcb7bb45a6be74307c 100644
--- a/src/core/SkCanvas.cpp
+++ b/src/core/SkCanvas.cpp
@@ -3098,11 +3098,10 @@ void SkCanvas::drawArc(const SkRect& oval, SkScalar startAngle,
                        SkScalar sweepAngle, bool useCenter,
                        const SkPaint& paint) {
     TRACE_EVENT0("disabled-by-default-skia", "SkCanvas::drawArc()");
-    if (SkScalarAbs(sweepAngle) >= SkIntToScalar(360)) {
-        this->drawOval(oval, paint);
-    } else {
-        this->onDrawArc(oval, startAngle, sweepAngle, useCenter, paint);
+    if (oval.isEmpty() || !sweepAngle) {
+        return;
     }
+    this->onDrawArc(oval, startAngle, sweepAngle, useCenter, paint);
 }
 
 void SkCanvas::drawTextOnPathHV(const void* text, size_t byteLength,