Changed progress indicator to use drawArc. (#5828)

Using paths' arcTo was causing performance issues in the Gallery.
This commit uses Skia's optimized drawArc in order to improve
performance, and it rolls the engine to the newest assing build.
Fixes #3599.

Tracking Skia issue:
  https://bugs.chromium.org/p/skia/issues/detail?id=5227

bin/cache/engine.version

-a55fa1efb90b83c56004f12ee67673f4836eb33d
+67888c599379a79c0b068bdc34a221ec500b2838

packages/flutter/lib/src/material/progress_indicator.dart

@@ -243,9 +243,7 @@ class _CircularProgressIndicatorPainter extends CustomPainter {
     if (value == null) // Indeterminate
       paint.strokeCap = StrokeCap.square;
 
-    Path path = new Path()
-      ..arcTo(Point.origin & size, arcStart, arcSweep, false);
-    canvas.drawPath(path, paint);
+    canvas.drawArc(Point.origin & size, arcStart, arcSweep, false, paint);
   }
 
   @override