Do not clear canvas with transparent color after creating SkSurface

third_party/WebKit/Source/platform/graphics/ImagePattern.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "platform/graphics/ImagePattern.h"
 
 #include "platform/graphics/Image.h"
 #include "platform/graphics/skia/SkiaUtils.h"
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "third_party/skia/include/core/SkImage.h"
@@ skipping 42 matching lines @@
     int expandH = isRepeatY() ? 0 : 1;
 
     // Create a transparent image 1 pixel wider and/or taller than the
     // original, then copy the orignal into it.
     // FIXME: Is there a better way to pad (not scale) an image in skia?
     sk_sp<SkSurface> surface = SkSurface::MakeRasterN32Premul(
         m_tileImage->width() + expandW, m_tileImage->height() + expandH);
     if (!surface)
         return SkShader::MakeColorShader(SK_ColorTRANSPARENT);
 
-    surface->getCanvas()->clear(SK_ColorTRANSPARENT);
     SkPaint paint;
     paint.setXfermodeMode(SkXfermode::kSrc_Mode);
     surface->getCanvas()->drawImage(m_tileImage, 0, 0, &paint);
 
     return surface->makeImageSnapshot()->makeShader(tileModeX, tileModeY, &localMatrix);
 }
 
 bool ImagePattern::isTextureBacked() const
 {
     return m_tileImage && m_tileImage->isTextureBacked();
 }
 
 } // namespace blink