Chromium -> Mojo roll.

cc/resources/layer_quad.cc

 // Copyright 2011 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.
 
 #include "cc/resources/layer_quad.h"
 
 #include "base/logging.h"
 #include "ui/gfx/geometry/quad_f.h"
 
 namespace cc {
 
 LayerQuad::Edge::Edge(const gfx::PointF& p, const gfx::PointF& q) {
   if (p == q) {
     degenerate_ = true;
     return;
   }
   degenerate_ = false;
   gfx::Vector2dF tangent(p.y() - q.y(), q.x() - p.x());
   float cross2 = p.x() * q.y() - q.x() * p.y();
 
   set(tangent.x(), tangent.y(), cross2);
   scale(1.0f / tangent.Length());
 }
 
+gfx::PointF LayerQuad::Edge::Intersect(const LayerQuad::Edge& e) const {
+  DCHECK(!degenerate());
+  DCHECK(!e.degenerate());
+
+  return gfx::PointF((y() * e.z() - e.y() * z()) / (x() * e.y() - e.x() * y()),
+                     (x() * e.z() - e.x() * z()) / (e.x() * y() - x() * e.y()));
+}
+
 LayerQuad::LayerQuad(const gfx::QuadF& quad) {
   // Create edges.
   left_ = Edge(quad.p4(), quad.p1());
   right_ = Edge(quad.p2(), quad.p3());
   top_ = Edge(quad.p1(), quad.p2());
   bottom_ = Edge(quad.p3(), quad.p4());
 
   float sign = quad.IsCounterClockwise() ? -1 : 1;
   left_.scale(sign);
   right_.scale(sign);
   top_.scale(sign);
   bottom_.scale(sign);
 }
 
 LayerQuad::LayerQuad(const Edge& left,
                      const Edge& top,
                      const Edge& right,
                      const Edge& bottom)
     : left_(left),
       top_(top),
       right_(right),
       bottom_(bottom) {}
 
 gfx::QuadF LayerQuad::ToQuadF() const {
+  size_t num_degenerate_edges = left_.degenerate() + right_.degenerate() +
+                                top_.degenerate() + bottom_.degenerate();
+  if (num_degenerate_edges > 1) {
+    return gfx::QuadF();
+  }
+
   if (left_.degenerate()) {
     return gfx::QuadF(top_.Intersect(bottom_), top_.Intersect(right_),
                       right_.Intersect(bottom_), bottom_.Intersect(top_));
   }
   if (right_.degenerate()) {
     return gfx::QuadF(left_.Intersect(top_), top_.Intersect(bottom_),
                       bottom_.Intersect(top_), bottom_.Intersect(left_));
   }
   if (top_.degenerate()) {
     return gfx::QuadF(left_.Intersect(right_), right_.Intersect(left_),
@@ skipping 42 matching lines @@
     flattened[10] = right_.y();
     flattened[11] = right_.z();
   } else {
     flattened[9] = bottom_.x();
     flattened[10] = bottom_.y();
     flattened[11] = bottom_.z();
   }
 }
 
 }  // namespace cc