DevTools: fix breakpoints rendering

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

 .CodeMirror {
     line-height: 1.2em !important;
     background-color: transparent !important;
 }
 
 .CodeMirror-linewidget {
     overflow: visible !important;
 }
 
 .CodeMirror-gutter-performance {
@@ skipping 62 matching lines @@
 
 .cm-breakpoint .CodeMirror-linenumber {
     color: white;
     border-width: 1px 4px 1px 1px !important;
     -webkit-border-image: url(Images/breakpoint.png) 1 4 1 1;
     margin: 0 0 0 3px !important;
     padding-right: 3px;
     padding-left: 1px;
     height: 11px;
     line-height: 12px !important;
+    border-style: solid;
 }
 
 .cm-line-without-source-mapping {
     background-color: #fafafa;
 }
 
 .cm-breakpoint.cm-breakpoint-conditional .CodeMirror-linenumber {
     -webkit-border-image: url(Images/breakpointConditional.png) 1 4 1 1;
 }
 
@@ skipping 251 matching lines @@
     background-color: rgba(255, 0, 0, 0.05);
 }
 
 .CodeMirror-activeline .cm-trailing-whitespace {
     background-color: transparent;
 }
 
 .-theme-with-dark-background .CodeMirror .CodeMirror-selected {
     background-color: #454545;
 }