Handle single pixel case on repeat bilerp.

src/core/SkLinearBitmapPipeline.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkLinearBitmapPipeline.h"
 
 #include <algorithm>
@@ skipping 349 matching lines @@
             // Convert to the Y0 bilerp sample set by shifting by -0.5f. Then tile that new y
             // value and shift it back resulting in the working Y0. Do the same thing with Y1 but
             // in the opposite direction.
             SkScalar y0 = fYStrategy.tileY(span.startY() - 0.5f) + 0.5f;
             SkScalar y1 = fYStrategy.tileY(span.startY() + 0.5f) - 0.5f;
             Span newSpan{{span.startX(), y0}, span.length(), span.count()};
             fNext->bilerpSpan(newSpan, y1);
         }
     }
     void breakIntoEdges(Span span) {
-        if (span.length() == 0) {
+        if (span.count() == 1) {
+            this->bilerpPoint(span.startX(), span.startY());
+        } else if (span.length() == 0) {
             yProcessSpan(span);
         } else {
             SkScalar dx = span.length() / (span.count() - 1);
             if (span.length() > 0) {
                 Span leftBorder = span.breakAt(0.5f, dx);
                 if (!leftBorder.isEmpty()) {
                     this->handleEdges(leftBorder, dx);
                 }
                 Span center = span.breakAt(fXMax - 0.5f, dx);
                 if (!center.isEmpty()) {
@@ skipping 580 matching lines @@
 void SkLinearBitmapPipeline::blitSpan(int x, int y, void* dst, int count) {
     SkASSERT(count > 0);
     fLastStage->setDestination(dst, count);
 
     // The count and length arguments start out in a precise relation in order to keep the
     // math correct through the different stages. Count is the number of pixel to produce.
     // Since the code samples at pixel centers, length is the distance from the center of the
     // first pixel to the center of the last pixel. This implies that length is count-1.
     fFirstStage->pointSpan(Span{{x + 0.5f, y + 0.5f}, count - 1.0f, count});
 }