Cherry pick two CLs back to M39 to fix a bug

src/utils/SkDashPath.cpp

Index: src/utils/SkDashPath.cpp
diff --git a/src/utils/SkDashPath.cpp b/src/utils/SkDashPath.cpp
index 3c4aef343d3399bbc8f30a846116063537499cea..4b2b33d2c4a1bf2ced56dcdd3d13ddf4772a0f29 100644
--- a/src/utils/SkDashPath.cpp
+++ b/src/utils/SkDashPath.cpp
@@ -115,14 +115,15 @@ static bool cull_path(const SkPath& srcPath, const SkStrokeRec& rec,
     SkScalar minX = pts[0].fX;
     SkScalar maxX = pts[1].fX;
 
-    if (maxX < bounds.fLeft || minX > bounds.fRight) {
-        return false;
-    }
-
     if (dx < 0) {
         SkTSwap(minX, maxX);
     }
 
+    SkASSERT(minX <= maxX);
+    if (maxX < bounds.fLeft || minX > bounds.fRight) {
+        return false;
+    }
+
     // Now we actually perform the chop, removing the excess to the left and
     // right of the bounds (keeping our new line "in phase" with the dash,
     // hence the (mod intervalLength).