Cherry pick two CLs back to M39 to fix a bug

src/utils/SkDashPath.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkDashPathPriv.h"
 #include "SkPathMeasure.h"
 
@@ skipping 97 matching lines @@
     SkScalar dy = pts[1].y() - pts[0].y();
 
     // just do horizontal lines for now (lazy)
     if (dy) {
         return false;
     }
 
     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).
 
     if (minX < bounds.fLeft) {
         minX = bounds.fLeft - SkScalarMod(bounds.fLeft - minX,
                                           intervalLength);
     }
     if (maxX > bounds.fRight) {
         maxX = bounds.fRight + SkScalarMod(maxX - bounds.fRight,
@@ skipping 183 matching lines @@
 bool SkDashPath::FilterDashPath(SkPath* dst, const SkPath& src, SkStrokeRec* rec,
                                 const SkRect* cullRect, const SkPathEffect::DashInfo& info) {
     SkScalar initialDashLength = 0;
     int32_t initialDashIndex = 0;
     SkScalar intervalLength = 0;
     CalcDashParameters(info.fPhase, info.fIntervals, info.fCount,
                        &initialDashLength, &initialDashIndex, &intervalLength);
     return FilterDashPath(dst, src, rec, cullRect, info.fIntervals, info.fCount, initialDashLength,
                           initialDashIndex, intervalLength);
 }