Fix erroneous comment on WebDialogDelegate::OnCloseContents()

The comment previously suggested that the contents passed in have already been
closed.  However, this is not true.  If |*out_close_dialog|
is set to true, the contents are then closed when the enclosing dialog is closed.
Otherwise, if the dialog is not closed, the contents are left intact.

Bug: 927957
Change-Id: Id9a4cdf70b10581aa4e8052093a7f0e6cae167b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1668334
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Danan S <danan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#670946}

ui/web_dialogs/web_dialog_delegate.h

@@ -105,9 +105,9 @@ class WEB_DIALOGS_EXPORT WebDialogDelegate {
   // response to a "dialogClose" message from WebUI.
   virtual void OnDialogCloseFromWebUI(const std::string& json_retval);
 
-  // A callback to notify the delegate that the contents have gone
-  // away. Only relevant if your dialog hosts code that calls
-  // windows.close() and you've allowed that.  If the output parameter
+  // A callback to notify the delegate that the contents are requesting
+  // to be closed.  This could be in response to a number of events
+  // that are handled by the WebContents.  If the output parameter
   // is set to true, then the dialog is closed.  The default is false.
   // |out_close_dialog| is never NULL.
   virtual void OnCloseContents(content::WebContents* source,