Don't add duplicate points when clipping

cc/base/math_util.cc

Index: cc/base/math_util.cc
diff --git a/cc/base/math_util.cc b/cc/base/math_util.cc
index d28c195971f6cd14eb753b6d9eddd51d1dd082fb..c29f75d7101348fff392cd55c9e658afee5c9523 100644
--- a/cc/base/math_util.cc
+++ b/cc/base/math_util.cc
@@ -158,6 +158,12 @@ static inline void ExpandBoundsToIncludePoint(float* xmin,
 static inline void AddVertexToClippedQuad(const gfx::PointF& new_vertex,
                                           gfx::PointF clipped_quad[8],
                                           int* num_vertices_in_clipped_quad) {
+  if (*num_vertices_in_clipped_quad > 0) {
+    if (clipped_quad[*num_vertices_in_clipped_quad - 1] == new_vertex)

[Peter Mayo, 2016/12/08 19:37:39]

These are floating point values, and should use an approximately equal to,
rather than absolute equality.

[flackr, 2016/12/08 20:24:01]

If the problem case is clipping to the same infinity do they not end up exactly
equal?

[Peter Mayo, 2016/12/08 20:29:09]

Inifinity is a single value in the non-parametric code, but becomes a vaguer
region in the parametric case - in order to stay planar in the 3d case.

+      return;
+    if (clipped_quad[0] == new_vertex)
+      return;
+  }
   clipped_quad[*num_vertices_in_clipped_quad] = new_vertex;
   (*num_vertices_in_clipped_quad)++;
 }
@@ -165,6 +171,12 @@ static inline void AddVertexToClippedQuad(const gfx::PointF& new_vertex,
 static inline void AddVertexToClippedQuad3d(const gfx::Point3F& new_vertex,
                                             gfx::Point3F clipped_quad[8],
                                             int* num_vertices_in_clipped_quad) {
+  if (*num_vertices_in_clipped_quad > 0) {
+    if (clipped_quad[*num_vertices_in_clipped_quad - 1] == new_vertex)
+      return;
+    if (clipped_quad[0] == new_vertex)
+      return;
+  }
   clipped_quad[*num_vertices_in_clipped_quad] = new_vertex;
   (*num_vertices_in_clipped_quad)++;
 }