DevTools: Reuse _showSourceLocation for execution line changes handling in sources panel

Source/devtools/front_end/cm/cmdevtools.css

 .CodeMirror * {
   box-sizing: content-box;
 }
 
 .CodeMirror {
   line-height: 1.2em !important;
   background-color: transparent !important;
 }
 
 .CodeMirror .source-frame-eval-expression {
@@ skipping 31 matching lines @@
 }
 
 .cm-highlight {
   -webkit-animation: "fadeout" 2s 0s;
 }
 @-webkit-keyframes fadeout {
     from {background-color: rgb(255, 255, 120); }
     to { background-color: white; }
 }
 
+.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-linenumber {
   color: white;
   border-width: 1px 4px 1px 1px !important;
   -webkit-border-image: url(Images/breakpoint.png) 1 4 1 1;
   margin: 0px 0px 0px 3px !important;
   padding-right: 3px;
   padding-left: 1px;
   height: 11px;
   line-height: 12px !important;
 }
@@ skipping 51 matching lines @@
     width: 90%;
     bottom: 50%;
     left: 5%;
 }
 
 .show-whitespaces .CodeMirror .cm-tab:before {
     display: block !important;
 }
 
 .cm-execution-line {
-    background-color: rgb(171, 191, 254) !important;
+    background-color: rgb(171, 191, 254);
     outline: 1px solid rgb(64, 115, 244);
 }
 
 .cm-execution-line .CodeMirror-linenumber {
     border-right: 1px solid rgb(64, 115, 244);
 }
 
 .cm-token-highlight {
     position: relative;
 }
@@ skipping 93 matching lines @@
 
 .CodeMirror .webkit-html-warning-message {
     background-color: rgb(100%, 62%, 42%);
     border: 2px solid rgb(100%, 52%, 21%);
 }
 
 .CodeMirror .webkit-html-error-message {
     background-color: rgb(100%, 42%, 42%);
     border: 2px solid rgb(100%, 31%, 31%);
 }