Scale focus outline thickness with zoom level.

third_party/WebKit/Source/core/style/ComputedStyle.cpp

Index: third_party/WebKit/Source/core/style/ComputedStyle.cpp
diff --git a/third_party/WebKit/Source/core/style/ComputedStyle.cpp b/third_party/WebKit/Source/core/style/ComputedStyle.cpp
index 2fc9f7e27dc9240c7390ee3a11a628a2d71227d6..9ffaa836a47b1a38607cece2204463f3e1d5c9bb 100644
--- a/third_party/WebKit/Source/core/style/ComputedStyle.cpp
+++ b/third_party/WebKit/Source/core/style/ComputedStyle.cpp
@@ -2184,12 +2184,23 @@ void ComputedStyle::setOffsetPath(PassRefPtr<StylePath> path) {
 int ComputedStyle::outlineOutsetExtent() const {
   if (!hasOutline())
     return 0;
-  if (outlineStyleIsAuto())
-    return GraphicsContext::focusRingOutsetExtent(outlineOffset(),
-                                                  outlineWidth());
+  if (outlineStyleIsAuto()) {
+    return GraphicsContext::focusRingOutsetExtent(
+        outlineOffset(), getOutlineStrokeWidthForFocusRing());
+  }
   return std::max(0, saturatedAddition(outlineWidth(), outlineOffset()));
 }
 
+float ComputedStyle::getOutlineStrokeWidthForFocusRing() const {
+#if OS(MACOSX)
+  return outlineWidth();
+#else
+  // Draw an outline with thickness in proportion to the zoom level, but never
+  // less than 1 pixel so that it remains visible.
+  return std::max(effectiveZoom(), 1.f);
+#endif
+}
+
 bool ComputedStyle::columnRuleEquivalent(
     const ComputedStyle* otherStyle) const {
   return columnRuleStyle() == otherStyle->columnRuleStyle() &&