Extend the geometry APIs.

mojo/services/geometry/interfaces/geometry.mojom

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 [DartPackage="mojo_services"]
 module mojo;
 
 struct Point {
   int32 x;
   int32 y;
@@ skipping 16 matching lines @@
   int32 height;
 };
 
 struct RectF {
   float x;
   float y;
   float width;
   float height;
 };
 
+struct RRect {
+  int32 x;
+  int32 y;
+  int32 width;
+  int32 height;
+  int32 top_left_radius_x;
+  int32 top_left_radius_y;
+  int32 top_right_radius_x;
+  int32 top_right_radius_y;
+  int32 bottom_left_radius_x;
+  int32 bottom_left_radius_y;
+  int32 bottom_right_radius_x;
+  int32 bottom_right_radius_y;

[abarth-chromium, 2015/12/10 22:49:53]

It's very common for all of these radii to have the same value.  In SkRRect,
there's a bunch of work to take faster paths for simpler cases.  If/when we
convert this class into an SkRRect, we should make sure we're still hitting
those fast paths.

[jeffbrown, 2015/12/11 19:40:55]

Skia auto-detects the type when provided with the more generalized set of
parameters.

I was debating whether to only support simple cases in the compositor but this
wasn't any more trouble and it makes for easier interop with Flutter's layer
system.  I expect we'll revisit this sooner or later depending on how things
work out.

+};
+
 struct Transform {
   // Row major order.
   array<float, 16> matrix;
 };