Program: 96738
Project: 96738
Buggy source:
GwtDisplayDevice(){
  canvas=Canvas.createIfSupported();
  if (canvas == null)   throw new UnsupportedOperationException("String_Node_Str");
  canvas.setCoordinateSpaceWidth(800);
  canvas.setCoordinateSpaceHeight(600);
  RootPanel.get().add(canvas);
  canvas.setFocus(true);
  boolean webgl2=WebGL20.isSupported();
  if (!webgl2 && !WebGL10.isSupported())   throw new UnsupportedOperationException("String_Node_Str");
  context=webgl2 ? WebGL20.createContext(canvas) : WebGL10.createContext(canvas);
  if (!webgl2)   if (!OES_vertex_array_object.isSupported())   throw new UnsupportedOperationException("String_Node_Str");
  WebGL10.glViewport(0,0,800,600);
  WebGL10.glClearColor(0,0,0,1);
  WebGL10.glClear(WebGL10.GL_COLOR_BUFFER_BIT);
  StyleElement style=Document.get().createStyleElement();
  style.setInnerHTML("String_Node_Str" + "String_Node_Str" + "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str");
  Document.get().getHead().appendChild(style);
  canvas.addKeyDownHandler(event -> checkRequestFullscreen());
  canvas.addKeyUpHandler(event -> checkRequestFullscreen());
  canvas.addKeyPressHandler(event -> checkRequestFullscreen());
  canvas.addMouseWheelHandler(event -> checkRequestFullscreen());
  canvas.addMouseMoveHandler(event -> checkRequestFullscreen());
  canvas.addMouseDownHandler(event -> checkRequestFullscreen());
  canvas.addMouseUpHandler(event -> checkRequestFullscreen());
  canvas.addTouchStartHandler(event -> checkRequestFullscreen());
  canvas.addTouchEndHandler(event -> checkRequestFullscreen());
  canvas.addTouchMoveHandler(event -> checkRequestFullscreen());
  canvas.addTouchCancelHandler(event -> checkRequestFullscreen());
  canvas.addFocusHandler(event -> focus=true);
  canvas.addBlurHandler(event -> focus=false);
  hookFocusCallbacks(this);
}

Fixed version (ground truth):
GwtDisplayDevice(){
  canvas=Canvas.createIfSupported();
  if (canvas == null)   throw new UnsupportedOperationException("String_Node_Str");
  canvas.setCoordinateSpaceWidth(800);
  canvas.setCoordinateSpaceHeight(600);
  RootPanel.get().add(canvas);
  canvas.setFocus(true);
  boolean webgl2=WebGL20.isSupported();
  if (!webgl2 && !WebGL10.isSupported())   throw new UnsupportedOperationException("String_Node_Str");
  context=webgl2 ? WebGL20.createContext(canvas) : WebGL10.createContext(canvas);
  if (!webgl2)   if (!OES_vertex_array_object.isSupported())   throw new UnsupportedOperationException("String_Node_Str");
  WebGL10.glViewport(0,0,800,600);
  WebGL10.glClearColor(0,0,0,1);
  WebGL10.glClear(WebGL10.GL_COLOR_BUFFER_BIT);
  StyleElement style=Document.get().createStyleElement();
  style.setInnerHTML("String_Node_Str" + "String_Node_Str" + "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str"+ "String_Node_Str");
  Document.get().getHead().appendChild(style);
  canvas.addKeyDownHandler(event -> checkRequestFullscreen());
  canvas.addKeyUpHandler(event -> checkRequestFullscreen());
  canvas.addKeyPressHandler(event -> checkRequestFullscreen());
  canvas.addMouseWheelHandler(event -> checkRequestFullscreen());
  canvas.addMouseMoveHandler(event -> checkRequestFullscreen());
  canvas.addMouseDownHandler(event -> checkRequestFullscreen());
  canvas.addMouseUpHandler(event -> checkRequestFullscreen());
  canvas.addTouchStartHandler(event -> checkRequestFullscreen());
  canvas.addTouchEndHandler(event -> checkRequestFullscreen());
  canvas.addTouchMoveHandler(event -> checkRequestFullscreen());
  canvas.addTouchCancelHandler(event -> checkRequestFullscreen());
  canvas.addFocusHandler(event -> focus=true);
  canvas.addBlurHandler(event -> focus=false);
  hookFocusCallbacks(this);
}