Prevent degenerate linear gradient instantiation

src/effects/gradients/SkGradientShader.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "Sk4fLinearGradient.h"
 #include "SkGradientShaderPriv.h"
 #include "SkLinearGradient.h"
@@ skipping 772 matching lines @@
     desc->fGradFlags    = flags;
     desc->fLocalMatrix  = localMatrix;
 }
 
 sk_sp<SkShader> SkGradientShader::MakeLinear(const SkPoint pts[2],
                                          const SkColor colors[],
                                          const SkScalar pos[], int colorCount,
                                          SkShader::TileMode mode,
                                          uint32_t flags,
                                          const SkMatrix* localMatrix) {
-    if (!pts) {
+    if (!pts || !SkScalarIsFinite((pts[1] - pts[0]).length())) {
         return nullptr;
     }
     if (!valid_grad(colors, pos, colorCount, mode)) {
         return nullptr;
     }
     EXPAND_1_COLOR(colorCount);
 
     SkGradientShaderBase::Descriptor desc;
     desc_init(&desc, colors, pos, colorCount, mode, flags, localMatrix);
     return sk_make_sp<SkLinearGradient>(pts, desc);
@@ skipping 404 matching lines @@
             (*stops)[i] = stop;
             stop = i < outColors - 1 ? stop + random->nextUScalar1() * (1.f - stop) : 1.f;
         }
     }
     *tm = static_cast<SkShader::TileMode>(random->nextULessThan(SkShader::kTileModeCount));
 
     return outColors;
 }
 
 #endif