Fix regression in inspector breakpoints.

third_party/WebKit/Source/devtools/front_end/devtools.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function(window) {
 
 // DevToolsAPI ----------------------------------------------------------------
 
 /**
  * @constructor
@@ skipping 974 matching lines @@
     function CSSPrimitiveValue()
     {
     }
     CSSPrimitiveValue.CSS_PX = 5;
     window.CSSPrimitiveValue = CSSPrimitiveValue;
 
     // Support for legacy (<M44) frontends. Remove in M48.
     var styleElement = window.document.createElement("style");
     styleElement.type = "text/css";
     styleElement.textContent = "html /deep/ * { min-width: 0; min-height: 0; }";
+
+    // Support for quirky border-image behavior (<M51), see:
+    // https://bugs.chromium.org/p/chromium/issues/detail?id=559258
+    styleElement.textContent += "\nhtml /deep/ .cm-breakpoint .CodeMirror-linenumber { border-style: solid !important; }";
+    styleElement.textContent += "\nhtml /deep/ .cm-breakpoint.cm-breakpoint-conditional .CodeMirror-linenumber { border-style: solid !important; }";
     window.document.head.appendChild(styleElement);
 
     // Support for legacy (<M49) frontends. Remove in M52.
     Event.prototype.deepPath = undefined;
 }
 
 function windowLoaded()
 {
     window.removeEventListener("DOMContentLoaded", windowLoaded, false);
     installBackwardsCompatibility();
 }
 
 if (window.document.head && (window.document.readyState === "complete" || window.document.readyState === "interactive"))
     installBackwardsCompatibility();
 else
     window.addEventListener("DOMContentLoaded", windowLoaded, false);
 
 })(window);
 
 if (!DOMTokenList.prototype.__originalDOMTokenListToggle) {
     DOMTokenList.prototype.__originalDOMTokenListToggle = DOMTokenList.prototype.toggle;
     DOMTokenList.prototype.toggle = function(token, force)
     {
         if (arguments.length === 1)
             force = !this.contains(token);
         return this.__originalDOMTokenListToggle(token, !!force);
     }
 }