[DevTools] chaotic green dots displacement fix

third_party/WebKit/Source/devtools/front_end/sources/JavaScriptSourceFrame.js

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 577 matching lines @@
     }
   }
 
   _showContinueToLocations() {
     var executionContext = UI.context.flavor(SDK.ExecutionContext);
     if (!executionContext)
       return;
     var callFrame = UI.context.flavor(SDK.DebuggerModel.CallFrame);
     if (!callFrame)
       return;
+    if (this._clearContinueToLocationsTimer) {
+      clearTimeout(this._clearContinueToLocationsTimer);
+      delete this._clearContinueToLocationsTimer;
+    }

[lushnikov, 2017/03/10 04:51:57]

Why don't we want greendots to be removed in case of absence of localScope?

Also, how is this fixing the race? Green dots will or will not be removed
depending on the timegap between _showContinueToLocations invocation.

[kozy, 2017/03/10 05:06:38]

Let me explain. When we clearExecutionLine we schedule green dots removing in 1
sec, if new execution line arrive before 1 second - we clear this timeout in
this function and show correct green dots, otherwise we cleanup green dots.
Issue was in the fact that we don't cancel green dots removing in case when
localScope is empty - e.g. scope when top level frame just inside of the script
and script doesn't have local variables by itself - but we should, otherwise
next time when we call show green dots - we override clear timeout with new one
and just never clear original one.

     var localScope = callFrame.localScope();
     if (!localScope)
       return;
     var start = localScope.startLocation();
     var end = localScope.endLocation();
     var debuggerModel = callFrame.debuggerModel;
     var executionLocation = callFrame.location();
     debuggerModel.getPossibleBreakpoints(start, end, true)
         .then(locations => this.textEditor.operation(renderLocations.bind(this, locations)));
 
-    if (this._clearContinueToLocationsTimer) {
-      clearTimeout(this._clearContinueToLocationsTimer);
-      delete this._clearContinueToLocationsTimer;
-    }
-
     /**
      * @param {!Array<!SDK.DebuggerModel.BreakLocation>} locations
      * @this {Sources.JavaScriptSourceFrame}
      */
     function renderLocations(locations) {
       var bookmarks = this.textEditor.bookmarks(
           this.textEditor.fullRange(), Sources.JavaScriptSourceFrame.continueToLocationDecorationSymbol);
       bookmarks.map(bookmark => bookmark.clear());
 
       for (var location of locations) {
@@ skipping 840 matching lines @@
       return;
     this.bookmark.clear();
     this.bookmark = null;
   }
 };
 
 Sources.JavaScriptSourceFrame.BreakpointDecoration.bookmarkSymbol = Symbol('bookmark');
 Sources.JavaScriptSourceFrame.BreakpointDecoration._elementSymbolForTest = Symbol('element');
 
 Sources.JavaScriptSourceFrame.continueToLocationDecorationSymbol = Symbol('bookmark');