--- a/browser/devtools/shared/Parser.jsm
+++ b/browser/devtools/shared/Parser.jsm
@@ -80,17 +80,17 @@ Parser.prototype = {
           syntaxTrees.push(new SyntaxTree(nodes, aUrl, length, offset));
         } catch (e) {
           this.errors.push(e);
           DevToolsUtils.reportException(aUrl, e);
         }
       }
     }
 
-    let pool = new SyntaxTreesPool(syntaxTrees, aUrl);
+    let pool = new SyntaxTreesPool(syntaxTrees);
 
     // Cache the syntax trees pool by the specified url. This is entirely
     // optional, but it's strongly encouraged to cache ASTs because
     // generating them can be costly with big/complex sources.
     if (aUrl) {
       this._cache.set(aUrl, pool);
     }
 
@@ -118,22 +118,19 @@ Parser.prototype = {
   errors: null
 };
 
 /**
  * A pool handling a collection of AST nodes generated by the reflection API.
  *
  * @param object aSyntaxTrees
  *        A collection of AST nodes generated for a source.
- * @param string aUrl [optional]
- *        The source url.
  */
-function SyntaxTreesPool(aSyntaxTrees, aUrl = "<unknown>") {
+function SyntaxTreesPool(aSyntaxTrees) {
   this._trees = aSyntaxTrees;
-  this._url = aUrl;
   this._cache = new Map();
 }
 
 SyntaxTreesPool.prototype = {
   /**
    * @see SyntaxTree.prototype.getIdentifierAt
    */
   getIdentifierAt: function({ line, column, scriptIndex }) {
@@ -213,17 +210,17 @@ SyntaxTreesPool.prototype = {
           parseResults.scriptLength = syntaxTree.length;
           parseResults.scriptOffset = syntaxTree.offset;
           results.push(parseResults);
         }
       } catch (e) {
         // Can't guarantee that the tree traversal logic is forever perfect :)
         // Language features may be added, in which case the recursive methods
         // need to be updated. If an exception is thrown here, file a bug.
-        DevToolsUtils.reportException("Syntax tree visitor for " + aUrl, e);
+        DevToolsUtils.reportException("syntax tree", e);
       }
     }
     this._cache.set(requestId, results);
     return results;
   },
 
   _trees: null,
   _cache: null

--- a/toolkit/devtools/DevToolsUtils.js
+++ b/toolkit/devtools/DevToolsUtils.js
@@ -24,17 +24,17 @@ this.safeErrorString = function safeErro
           let stack = aError.stack.toString();
           if (typeof stack == "string") {
             errorString += "\nStack: " + stack;
           }
         }
       } catch (ee) { }
 
       if (typeof aError.lineNumber == "number" && typeof aError.columnNumber == "number") {
-        errorString += "Line: " + aError.lineNumber + ", column: " + aError.columnNumber;
+        errorString += ", line: " + aError.lineNumber + ", column: " + aError.columnNumber;
       }
 
       return errorString;
     }
   } catch (ee) { }
 
   return "<failed trying to find error description>";
 }