add drawCircle to c api

BUG=skia:4927
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1684763002

TBR=

Review URL: https://codereview.chromium.org/1684763002
diff --git a/src/c/sk_surface.cpp b/src/c/sk_surface.cpp
index b8fbc63..6618881 100644
--- a/src/c/sk_surface.cpp
+++ b/src/c/sk_surface.cpp
@@ -375,6 +375,11 @@
     AsCanvas(ccanvas)->drawRect(AsRect(*crect), AsPaint(*cpaint));
 }
 
+void sk_canvas_draw_circle(sk_canvas_t* ccanvas, float cx, float cy, float rad,
+                           const sk_paint_t* cpaint) {
+    AsCanvas(ccanvas)->drawCircle(cx, cy, rad, AsPaint(*cpaint));
+}
+
 void sk_canvas_draw_oval(sk_canvas_t* ccanvas, const sk_rect_t* crect, const sk_paint_t* cpaint) {
     AsCanvas(ccanvas)->drawOval(AsRect(*crect), AsPaint(*cpaint));
 }