Add pointer-events="bounding-box" for svg content.

Source/core/css/CSSPrimitiveValueMappings.h

Index: Source/core/css/CSSPrimitiveValueMappings.h
diff --git a/Source/core/css/CSSPrimitiveValueMappings.h b/Source/core/css/CSSPrimitiveValueMappings.h
index 41cf0a7930f2f0cf392ee14a4c6852a58aa9f16c..232bb5cedf040437d4b3bcd59e972e09095745b8 100644
--- a/Source/core/css/CSSPrimitiveValueMappings.h
+++ b/Source/core/css/CSSPrimitiveValueMappings.h
@@ -3348,6 +3348,9 @@ template<> inline CSSPrimitiveValue::CSSPrimitiveValue(EPointerEvents e)
     case PE_ALL:
         m_value.valueID = CSSValueAll;
         break;
+    case PE_BOUNDINGBOX:
+        m_value.valueID = CSSValueBoundingbox;
+        break;
     }
 }
 
@@ -3375,6 +3378,8 @@ template<> inline CSSPrimitiveValue::operator EPointerEvents() const
         return PE_FILL;
     case CSSValueStroke:
         return PE_STROKE;
+    case CSSValueBoundingbox:
+        return PE_BOUNDINGBOX;
     default:
         break;
     }