hide trivial helpers on canvas

BUG=skia:

Change-Id: I42d4ca92897bde5bd8e0575a0104b12b83134cef
Reviewed-on: https://skia-review.googlesource.com/8852
Reviewed-by: Cary Clark <caryclark@google.com>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/gm/aaa.cpp b/gm/aaa.cpp
index 8893744..614ff84 100644
--- a/gm/aaa.cpp
+++ b/gm/aaa.cpp
@@ -39,15 +39,15 @@
 
         canvas->translate(0, y);
         canvas->rotate(1);
-        canvas->drawRectCoords(20, 20, 200, 200, p);
+        canvas->drawRect({ 20, 20, 200, 200 }, p);
         canvas->restore();
 
         y += 200;
 
         canvas->translate(0, y);
         canvas->rotate(1);
-        canvas->drawRectCoords(20, 20, 20.2f, 200, p);
-        canvas->drawRectCoords(20, 200, 200, 200.1f, p);
+        canvas->drawRect({ 20, 20, 20.2f, 200 }, p);
+        canvas->drawRect({ 20, 200, 200, 200.1f }, p);
         canvas->drawCircle(100, 100, 30, p);
         canvas->restore();