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

Source/devtools/front_end/cm/css.js

 CodeMirror.defineMode("css", function(config) {
   return CodeMirror.getMode(config, "text/css");
 });
 
 CodeMirror.defineMode("css-base", function(config, parserConfig) {
   "use strict";
 
   var indentUnit = config.indentUnit,
       hooks = parserConfig.hooks || {},
       atMediaTypes = parserConfig.atMediaTypes || {},
@@ skipping 424 matching lines @@
     "whitesmoke", "yellow", "yellowgreen"
   ]);
 
   var valueKeywords = keySet([
     "above", "absolute", "activeborder", "activecaption", "afar",
     "after-white-space", "ahead", "alias", "all", "all-scroll", "alternate",
     "always", "amharic", "amharic-abegede", "antialiased", "appworkspace",
     "arabic-indic", "armenian", "asterisks", "auto", "avoid", "background",
     "backwards", "baseline", "below", "bidi-override", "binary", "bengali",
     "blink", "block", "block-axis", "bold", "bolder", "border", "border-box",
-    "both", "bottom", "break-all", "break-word", "button", "button-bevel",
+    "both", "bottom", "bounding-box", "break-all", "break-word", "button", "button-bevel",
     "buttonface", "buttonhighlight", "buttonshadow", "buttontext", "cambodian",
     "capitalize", "caps-lock-indicator", "caption", "captiontext", "caret",
     "cell", "center", "checkbox", "circle", "cjk-earthly-branch",
     "cjk-heavenly-stem", "cjk-ideographic", "clear", "clip", "close-quote",
     "col-resize", "collapse", "compact", "condensed", "contain", "content",
     "content-box", "context-menu", "continuous", "copy", "cover", "crop",
     "cross", "crosshair", "currentcolor", "cursive", "dashed", "decimal",
     "decimal-leading-zero", "default", "default-button", "destination-atop",
     "destination-in", "destination-out", "destination-over", "devanagari",
     "disc", "discard", "document", "dot-dash", "dot-dot-dash", "dotted",
@@ skipping 142 matching lines @@
           return ["operator", "interpolation"];
         } else {
           stream.eatWhile(/[\w\\\-]/);
           return ["atom", "hash"];
         }
       }
     },
     name: "css-base"
   });
 })();