Bug 1251823 - fix adding breakpoints through context menu in debugger r=me

devtools/client/debugger/content/views/sources-view.js

@@ -1147,7 +1147,7 @@ SourcesView.prototype = Heritage.extend(WidgetMethods, {
    */
   _onCmdAddBreakpoint: function(e) {
     let actor = this.selectedValue;
-    let line = (e && e.sourceEvent.target.tagName == 'menuitem' ?
+    let line = (this.DebuggerView.clickedLine ?
                 this.DebuggerView.clickedLine + 1 :
                 this.DebuggerView.editor.getCursor().line + 1);
     let location = { actor, line };

devtools/client/debugger/debugger-view.js

@@ -337,6 +337,10 @@ var DebuggerView = {
         }
       }
     });
+
+    this.editor.on("cursorActivity", () => {
+      this.clickedLine = null;
+    });
   },
 
   updateEditorBreakpoints: function(source) {