Use stable sort for Viewer's help screen

Fixes flickering help text

Change-Id: I61159e6946125e9e2ce7be3f8f8f6103473855be
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/302266
Commit-Queue: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: Brian Osman <brianosman@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>

Author: brianosman

tools/sk_app/CommandSet.cpp

@@ -99,8 +99,8 @@ void CommandSet::drawHelp(SkCanvas* canvas) {
     }
 
     // Sort commands for current mode:
-    SkTQSort(fCommands.begin(), fCommands.end() - 1,
-             kAlphabetical_HelpMode == fHelpMode ? compareCommandKey : compareCommandGroup);
+    std::stable_sort(fCommands.begin(), fCommands.end(),
+                     kAlphabetical_HelpMode == fHelpMode ? compareCommandKey : compareCommandGroup);
 
     SkFont font;
     font.setSize(16);