Harden linear gradients

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 756 matching lines @@
             tmp[0] = tmp[1] = colors[0];    \
             colors = tmp;                   \
             pos = nullptr;                     \
             count = 2;                      \
         }                                   \
     } while (0)
 
 static void desc_init(SkGradientShaderBase::Descriptor* desc,
                       const SkColor colors[], const SkScalar pos[], int colorCount,
                       SkShader::TileMode mode, uint32_t flags, const SkMatrix* localMatrix) {
+    SkASSERT(colorCount > 1);
+
     desc->fColors       = colors;
     desc->fPos          = pos;
     desc->fCount        = colorCount;
     desc->fTileMode     = mode;
     desc->fGradFlags    = flags;
     desc->fLocalMatrix  = localMatrix;
 }
 
 sk_sp<SkShader> SkGradientShader::MakeLinear(const SkPoint pts[2],
                                          const SkColor colors[],
@@ skipping 416 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