Support 'paint-order' from SVG2.

Source/core/page/UseCounter.cpp

Index: Source/core/page/UseCounter.cpp
diff --git a/Source/core/page/UseCounter.cpp b/Source/core/page/UseCounter.cpp
index 57f7c0cc9d16ecac674e8ec030856641dcca447e..0ce378ae442b0591d32e4a6d651252f16b9fb87a 100644
--- a/Source/core/page/UseCounter.cpp
+++ b/Source/core/page/UseCounter.cpp
@@ -493,6 +493,7 @@ int UseCounter::mapCSSPropertyIdToCSSSampleIdForHistogram(int id)
     case CSSPropertyAnimationPlayState: return 431;
     case CSSPropertyAnimationTimingFunction: return 432;
     case CSSPropertyObjectFit: return 433;
+    case CSSPropertyPaintOrder: return 434;
 
     // Add new features above this line (don't change the assigned numbers of the existing
     // items) and update maximumCSSSampleId() with the new maximum value.
@@ -507,7 +508,7 @@ int UseCounter::mapCSSPropertyIdToCSSSampleIdForHistogram(int id)
     return 0;
 }
 
-static int maximumCSSSampleId() { return 433; }
+static int maximumCSSSampleId() { return 434; }
 
 UseCounter::UseCounter()
 {