Reusing base::IdType<...> to implement SurfaceId.

cc/test/surface_aggregator_test_helpers.cc

Index: cc/test/surface_aggregator_test_helpers.cc
diff --git a/cc/test/surface_aggregator_test_helpers.cc b/cc/test/surface_aggregator_test_helpers.cc
index 05e54b7a41348fe7bafa69ea7da50308f7da34d9..4b4eccb8913459f3d1f8b7dc05398d4111ab651d 100644
--- a/cc/test/surface_aggregator_test_helpers.cc
+++ b/cc/test/surface_aggregator_test_helpers.cc
@@ -21,6 +21,34 @@
 namespace cc {
 namespace test {
 
+Quad::Quad()
+    : material(DrawQuad::INVALID), opacity(1.f), color(SK_ColorWHITE) {}
+
+// static
+Quad Quad::SolidColorQuad(SkColor color) {
+  Quad quad;
+  quad.material = DrawQuad::SOLID_COLOR;
+  quad.color = color;
+  return quad;
+}
+
+// static
+Quad Quad::SurfaceQuad(SurfaceId surface_id, float opacity) {
+  Quad quad;
+  quad.material = DrawQuad::SURFACE_CONTENT;
+  quad.opacity = opacity;
+  quad.surface_id = surface_id;
+  return quad;
+}
+
+// static
+Quad Quad::RenderPassQuad(RenderPassId id) {
+  Quad quad;
+  quad.material = DrawQuad::RENDER_PASS;
+  quad.render_pass_id = id;
+  return quad;
+}
+
 void AddSurfaceQuad(RenderPass* pass,
                     const gfx::Size& surface_size,
                     float opacity,