Make SVG images for custom CSS cursors appear sharp on retina displays

Source/core/platform/Cursor.cpp

Index: Source/core/platform/Cursor.cpp
===================================================================
--- Source/core/platform/Cursor.cpp	(revision 162906)
+++ Source/core/platform/Cursor.cpp	(working copy)
@@ -25,6 +25,7 @@
 
 #include "config.h"
 #include "core/platform/Cursor.h"
+#include "core/platform/graphics/ImageBuffer.h"
 
 namespace WebCore {
 
@@ -47,6 +48,27 @@
     return IntPoint();
 }
 
+// Similar to Image::nativeImageForCurrentFrame() but incorporates the image
+// scale factor. This ensures that SVG cursors are sharp at high DPI settings.
+Cursor rasterizeSVGCursor(const Cursor& cursor, float imageScaleFactor)
+{
+    Image* image = cursor.image();
+    if (!image || !image->isSVGImage() || imageScaleFactor == 1)
+        return cursor;
+
+    IntSize size = image->size();
+    IntPoint hotSpot = cursor.hotSpot();
+    size.scale(imageScaleFactor);
+    hotSpot.scale(imageScaleFactor, imageScaleFactor);
+
+    OwnPtr<ImageBuffer> buffer = ImageBuffer::create(size, 1);
+    if (!buffer) // failed to allocate image
+        return cursor;
+
+    buffer->context()->drawImage(image, FloatRect(IntRect(IntPoint(), size)));
+    return Cursor(buffer->copyImage(DontCopyBackingStore).get(), hotSpot, imageScaleFactor);
+}
+
 const Cursor& Cursor::fromType(Cursor::Type type)
 {
     switch (type) {