Bug 1595038 - Add a planeNormal variable so that it's clear that the same plane is used for the entire inner loop. r=kip

Differential Revision: https://phabricator.services.mozilla.com/D68702

--HG--
extra : moz-landing-system : lando

gfx/2d/Matrix.h

@@ -861,7 +861,8 @@ class Matrix4x4Typed {
     // current clipped polygon. We double buffer that set of points, alternating
     // between points[0] and points[1].
     for (int plane = 0; plane < 4; plane++) {
-      planeNormals[plane].Normalize();
+      auto planeNormal = planeNormals[plane];
+      planeNormal.Normalize();
       Point4DTyped<UnknownUnits, F>* srcPoint = dstPointStart;
       Point4DTyped<UnknownUnits, F>* srcPointEnd = dstPoint;
 
@@ -877,10 +878,10 @@ class Matrix4x4Typed {
       // We may create duplicated points in the polygon. We keep those around
       // until all clipping is done and then filter out duplicates at the end.
       Point4DTyped<UnknownUnits, F>* prevPoint = srcPointEnd - 1;
-      F prevDot = planeNormals[plane].DotProduct(*prevPoint);
+      F prevDot = planeNormal.DotProduct(*prevPoint);
       while (srcPoint < srcPointEnd &&
              ((dstPoint - dstPointStart) < kTransformAndClipRectMaxVerts)) {
-        F nextDot = planeNormals[plane].DotProduct(*srcPoint);
+        F nextDot = planeNormal.DotProduct(*srcPoint);
 
         if ((nextDot >= 0.0) != (prevDot >= 0.0)) {
           // An intersection with the clipping plane has been detected.