DevTools: NOOP if outline dialog is not available for the content type

Source/devtools/front_end/sources/SourcesView.js

Index: Source/devtools/front_end/sources/SourcesView.js
diff --git a/Source/devtools/front_end/sources/SourcesView.js b/Source/devtools/front_end/sources/SourcesView.js
index 178ec2f9354967ef8b739017523d56450a219db3..c21a287b156f43556a4afdac6c231ddd84e26515 100644
--- a/Source/devtools/front_end/sources/SourcesView.js
+++ b/Source/devtools/front_end/sources/SourcesView.js
@@ -611,8 +611,10 @@ WebInspector.SourcesView.prototype = {
         case WebInspector.resourceTypes.Stylesheet:
             WebInspector.StyleSheetOutlineDialog.show(this, uiSourceCode, this.showSourceLocation.bind(this, uiSourceCode));
             return true;
+        default:
+            // We don't want default browser shortcut to be executed, so pretend to handle this event.
+            return true;
         }
-        return false;
     },
 
     /**