Let page zoom affect resolution and -webkit-device-pixel-ratio MQs.

Source/core/page/Frame.cpp

Index: Source/core/page/Frame.cpp
diff --git a/Source/core/page/Frame.cpp b/Source/core/page/Frame.cpp
index 976fb169caf19f9072f1bee77d2af9430bb496ef..adbe6d3cb027b55780220963ad268a5021fcb280 100644
--- a/Source/core/page/Frame.cpp
+++ b/Source/core/page/Frame.cpp
@@ -709,4 +709,15 @@ PassOwnPtr<DragImage> Frame::dragImageForSelection()
     return DragImage::create(image.get());
 }
 
+double Frame::devicePixelRatio() const
+{
+    if (!m_page)
+        return 0;
+
+    double ratio = m_page->deviceScaleFactor();
+    if (RuntimeEnabledFeatures::devicePixelRatioIncludesZoomEnabled())
+        ratio *= pageZoomFactor();
+    return ratio;
+}
+
 } // namespace WebCore