DevTools: Modify shadow-editor canvas colors to work better with dark theme

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

 // Copyright 2016 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.
 
 /**
  * @constructor
  * @extends {WebInspector.VBox}
  */
 WebInspector.CSSShadowEditor = function()
 {
@@ skipping 121 matching lines @@
      * @param {boolean} drawFocus
      */
     _updateCanvas: function(drawFocus)
     {
         var context = this._xySlider.getContext("2d");
         context.clearRect(0, 0, this._xySlider.width, this._xySlider.height);
 
         // Draw dashed axes.
         context.save();
         context.setLineDash([1, 1]);
-        context.strokeStyle = "rgba(0, 0, 0, 0.2)";
+        context.strokeStyle = "rgba(210, 210, 210, 0.8)";
         context.beginPath();
         context.moveTo(this._halfCanvasSize, 0);
         context.lineTo(this._halfCanvasSize, WebInspector.CSSShadowEditor.canvasSize);
         context.moveTo(0, this._halfCanvasSize);
         context.lineTo(WebInspector.CSSShadowEditor.canvasSize, this._halfCanvasSize);
         context.stroke();
         context.restore();
 
         var thumbPoint = this._sliderThumbPosition();
         // Draw 2D slider line.
         context.save();
         context.translate(this._halfCanvasSize, this._halfCanvasSize);
         context.lineWidth = 2;
-        context.strokeStyle = "rgba(0, 0, 0, 0.3)";
+        context.strokeStyle = "rgba(130, 130, 130, 0.75)";
         context.beginPath();
         context.moveTo(0, 0);
         context.lineTo(thumbPoint.x, thumbPoint.y);
         context.stroke();
         // Draw 2D slider thumb.
         if (drawFocus) {
             context.beginPath();
             context.fillStyle = "rgba(66, 133, 244, 0.4)";
             context.arc(thumbPoint.x, thumbPoint.y, WebInspector.CSSShadowEditor.sliderThumbRadius + 2, 0, 2 * Math.PI);
             context.fill();
@@ skipping 266 matching lines @@
      */
     _sliderThumbPosition: function()
     {
         var x = (this._model.offsetX().amount / WebInspector.CSSShadowEditor.maxRange) * this._innerCanvasSize;
         var y = (this._model.offsetY().amount / WebInspector.CSSShadowEditor.maxRange) * this._innerCanvasSize;
         return this._constrainPoint(new WebInspector.Geometry.Point(x, y), this._innerCanvasSize);
     },
 
     __proto__: WebInspector.VBox.prototype
 }