Don't turn off anti-aliasing for image backgrounds unless the device scale factor is large enough.

Source/core/rendering/RenderImage.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011-2012. All rights reserved.
  *
@@ skipping 20 matching lines @@
 #include "core/HTMLNames.h"
 #include "core/editing/FrameSelection.h"
 #include "core/fetch/ImageResource.h"
 #include "core/fetch/ResourceLoadPriorityOptimizer.h"
 #include "core/fetch/ResourceLoader.h"
 #include "core/frame/LocalFrame.h"
 #include "core/html/HTMLAreaElement.h"
 #include "core/html/HTMLImageElement.h"
 #include "core/html/HTMLInputElement.h"
 #include "core/html/HTMLMapElement.h"
+#include "core/page/Page.h"
 #include "core/paint/ImagePainter.h"
 #include "core/rendering/HitTestResult.h"
 #include "core/rendering/PaintInfo.h"
 #include "core/rendering/RenderLayer.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/TextRunConstructor.h"
 #include "core/svg/graphics/SVGImage.h"
 #include "platform/fonts/Font.h"
 #include "platform/fonts/FontCache.h"
 
 namespace blink {
 
-float deviceScaleFactor(LocalFrame*);
-
 using namespace HTMLNames;
 
 RenderImage::RenderImage(Element* element)
     : RenderReplaced(element, IntSize())
     , m_didIncrementVisuallyNonEmptyPixelCount(false)
     , m_isGeneratedContent(false)
     , m_imageDevicePixelRatio(1.0f)
 {
     updateAltText();
     ResourceLoadPriorityOptimizer::resourceLoadPriorityOptimizer()->addRenderObject(this);
@@ skipping 399 matching lines @@
         return 0;
 
     ImageResource* cachedImage = m_imageResource->cachedImage();
     if (cachedImage && cachedImage->image() && cachedImage->image()->isSVGImage())
         return toSVGImage(cachedImage->image())->embeddedContentBox();
 
     return 0;
 }
 
 } // namespace blink