[DevTools] Make line highlight stay in readonly editor.

third_party/WebKit/Source/devtools/front_end/text_editor/cmdevtools.css

 .CodeMirror {
     line-height: 1.2em !important;
     background-color: transparent !important;
     color: #222;
 }
 
 .CodeMirror-linewidget {
     overflow: visible !important;
 }
 
@@ skipping 52 matching lines @@
 }
 @-webkit-keyframes fadeout {
     from {background-color: rgb(255, 255, 120); }
     to { background-color: white; }
 }
 @-webkit-keyframes fadeout-dark {
     from {background-color: hsla(133, 100%, 30%, 0.5); }
     to { background-color: transparent; }
 }
 
+.cm-readonly-highlight {
+    background-color: rgb(255, 255, 120);
+}
+
+.-theme-with-dark-background .cm-readonly-highlight {
+    background-color: hsla(133, 100%, 30%, 0.5);
+}
+
 .cm-highlight.cm-execution-line {
     -webkit-animation: fadeout-execution-line 1s 0s;
 }
 @-webkit-keyframes fadeout-execution-line {
     from {background-color: rgb(121, 141, 254); }
     to { background-color: rgb(171, 191, 254); }
 }
 
 .cm-breakpoint .CodeMirror-gutter-wrapper .CodeMirror-linenumber {
     color: white;
@@ skipping 288 matching lines @@
     margin-right: 0.5em;
 }
 
 .CodeMirror .text-editor-line-decoration-icon {
     position: absolute;
     cursor: pointer;
     right: -16px;
     top: -9px;
 }
 
-.CodeMirror .text-editor-line-with-warning:not(.cm-execution-line) {
+.CodeMirror .text-editor-line-with-warning:not(.cm-execution-line):not(.cm-readonly-highlight) {
     background-color: rgba(241, 230, 0, 0.1);
 }
 
-.CodeMirror .text-editor-line-with-error:not(.cm-execution-line) {
+.CodeMirror .text-editor-line-with-error:not(.cm-execution-line):not(.cm-readonly-highlight) {
     background-color: rgba(255, 0, 0, 0.05);
 }
 
 .CodeMirror .text-editor-line-decoration-wave {
     background-image: url(Images/errorWave.png);
     background-repeat: repeat-x;
     background-size: contain;
 }
 
 @media (-webkit-min-device-pixel-ratio: 1.1) {
@@ skipping 25 matching lines @@
 
 .CodeMirror .auto-complete-text {
     color: rgb(128,128,128);
 }
 
 /** Prevent the codemirror textarea from stealing PageUp events **/
 .CodeMirror textarea {
     resize: none;
     overflow: hidden;
 }