cc: Turn SharedQuadState into a struct-like class similar to DrawQuads.

cc/test/layer_test_common.cc

Index: cc/test/layer_test_common.cc
diff --git a/cc/test/layer_test_common.cc b/cc/test/layer_test_common.cc
index 2156dc828a21e540cbd47b255e40dfe2e92bf6ed..6b456f8b1e5579742834d26918d1b2d12a39cb2e 100644
--- a/cc/test/layer_test_common.cc
+++ b/cc/test/layer_test_common.cc
@@ -38,7 +38,7 @@ void verifyQuadsExactlyCoverRect(const cc::QuadList& quads,
 
     for (size_t i = 0; i < quads.size(); ++i) {
         cc::DrawQuad* quad = quads[i];
-        gfx::RectF quadRectF = cc::MathUtil::mapClippedRect(quad->shared_quad_state->quadTransform, gfx::RectF(quad->rect));
+        gfx::RectF quadRectF = cc::MathUtil::mapClippedRect(quad->quadTransform(), gfx::RectF(quad->rect));
 
         // Before testing for exact coverage in the integer world, assert that rounding
         // will not round the rect incorrectly.