Support the DPR header for client hints.

Source/core/rendering/RenderImage.cpp

Index: Source/core/rendering/RenderImage.cpp
diff --git a/Source/core/rendering/RenderImage.cpp b/Source/core/rendering/RenderImage.cpp
index 70479a835c204afbd75a74ad2dd458de0497dcaa..5f58a39fe7306570beb37b34380198669dc5cde0 100644
--- a/Source/core/rendering/RenderImage.cpp
+++ b/Source/core/rendering/RenderImage.cpp
@@ -164,6 +164,9 @@ void RenderImage::imageChanged(WrappedImagePtr newImage, const IntRect* rect)
     if (newImage != m_imageResource->imagePtr())
         return;
 
+    if (m_imageResource->cachedImage() && m_imageResource->cachedImage()->hasDprHeaderValue())
+        m_imageDevicePixelRatio = 1 / m_imageResource->cachedImage()->dprHeaderValue();
+
     if (!m_didIncrementVisuallyNonEmptyPixelCount) {
         // At a zoom level of 1 the image is guaranteed to have an integer size.
         view()->frameView()->incrementVisuallyNonEmptyPixelCount(flooredIntSize(m_imageResource->imageSize(1.0f)));