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

src/gpu/GrOvalRenderer.cpp

Index: src/gpu/GrOvalRenderer.cpp
diff --git a/src/gpu/GrOvalRenderer.cpp b/src/gpu/GrOvalRenderer.cpp
index f32168e945883333e6e838ed5d4fea9368ac0372..f6176b5f7817f47c36c495b244a6eb6c319e01a3 100644
--- a/src/gpu/GrOvalRenderer.cpp
+++ b/src/gpu/GrOvalRenderer.cpp
@@ -1899,7 +1899,12 @@ GrDrawBatch* GrOvalRenderer::CreateArcBatch(GrColor color,
                                             bool useCenter,
                                             const GrStyle& style,
                                             const GrShaderCaps* shaderCaps) {
+    SkASSERT(!oval.isEmpty());
+    SkASSERT(sweepAngle);
     SkScalar width = oval.width();
+    if (SkScalarAbs(sweepAngle) >= 360.f) {
+        return nullptr;
+    }
     if (!SkScalarNearlyEqual(width, oval.height()) || !circle_stays_circle(viewMatrix)) {
         return nullptr;
     }