Do not clear canvas with transparent color after creating SkSurface

third_party/WebKit/Source/platform/DragImage.cpp

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 89 matching lines @@
     if (!surface)
         return nullptr;
 
     SkPaint paint;
     ASSERT(opacity >= 0 && opacity <= 1);
     paint.setAlpha(opacity * 255);
     paint.setFilterQuality(interpolationQuality == InterpolationNone
         ? kNone_SkFilterQuality : kHigh_SkFilterQuality);
 
     SkCanvas* canvas = surface->getCanvas();
-    canvas->clear(SK_ColorTRANSPARENT);
     canvas->concat(affineTransformToSkMatrix(transform));
     canvas->drawImage(image.get(), 0, 0, &paint);
 
     return fromSkSp(surface->makeImageSnapshot());
 }
 
 FloatSize DragImage::clampedImageScale(const IntSize& imageSize, const IntSize& size,
     const IntSize& maxSize)
 {
     // Non-uniform scaling for size mapping.
@@ skipping 147 matching lines @@
 
 void DragImage::scale(float scaleX, float scaleY)
 {
     skia::ImageOperations::ResizeMethod resizeMethod = m_interpolationQuality == InterpolationNone ? skia::ImageOperations::RESIZE_BOX : skia::ImageOperations::RESIZE_LANCZOS3;
     int imageWidth = scaleX * m_bitmap.width();
     int imageHeight = scaleY * m_bitmap.height();
     m_bitmap = skia::ImageOperations::Resize(m_bitmap, resizeMethod, imageWidth, imageHeight);
 }
 
 } // namespace blink