DevTools: set a default color for icon masks

This patch sets a default color for icon masks. This should be good
enough to solve concerns in https://crrev.com/2570783006 while supporting
dark theme.

BUG=669323
R=dgozman

Review-Url: https://codereview.chromium.org/2572283002
Cr-Commit-Position: refs/heads/master@{#438761}

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

@@ -312,7 +312,7 @@ Console.ConsoleViewMessage = class {
     var contentElement = toggleElement.createChild('div', 'console-message-stack-trace-wrapper');
 
     var messageElement = this._buildMessage(consoleMessage);
-    var icon = UI.Icon.create('smallicon-triangle-right', 'stack-trace-expand-icon');
+    var icon = UI.Icon.create('smallicon-triangle-right');
     var clickableElement = contentElement.createChild('div');
     clickableElement.appendChild(icon);
 

third_party/WebKit/Source/devtools/front_end/console/consoleView.css

@@ -366,7 +366,3 @@
 .console-message-stack-trace-wrapper > * {
     flex: none;
 }
-
-.stack-trace-expand-icon {
-    background-color: rgb(110, 110, 110);
-}

third_party/WebKit/Source/devtools/front_end/ui/inspectorCommon.css

@@ -327,6 +327,10 @@ label[is=dt-icon-label] {
     flex-shrink: 0;
 }
 
+.icon-mask {
+    background-color: rgb(110, 110, 110);
+}
+
 .spritesheet-smallicons {
     background-image: -webkit-image-set(url(Images/smallIcons.png) 1x, url(Images/smallIcons_2x.png) 2x);
     background-size: 190px 30px;