[CSS Grid Layout] infinity should be defined as a negative value

Source/core/rendering/RenderGrid.cpp

 /*
  * Copyright (C) 2011 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 15 matching lines @@
 #include "config.h"
 #include "core/rendering/RenderGrid.h"
 
 #include "core/rendering/LayoutRepainter.h"
 #include "core/rendering/RenderLayer.h"
 #include "core/rendering/RenderView.h"
 #include "core/rendering/style/GridCoordinate.h"
 
 namespace WebCore {
 
-static const int infinity = intMaxForLayoutUnit;
+static const int infinity = -1;
 
 class GridTrack {
 public:
     GridTrack()
         : m_usedBreadth(0)
         , m_maxBreadth(0)
     {
     }
 
     void growUsedBreadth(LayoutUnit growth)
@@ skipping 300 matching lines @@
 
 LayoutUnit RenderGrid::computeUsedBreadthOfMaxLength(TrackSizingDirection direction, const GridLength& gridLength, LayoutUnit usedBreadth) const
 {
     if (gridLength.isFlex())
         return usedBreadth;
 
     const Length& trackLength = gridLength.length();
     ASSERT(!trackLength.isAuto());
     if (trackLength.isFixed() || trackLength.isPercent() || trackLength.isViewportPercentage()) {
         LayoutUnit computedBreadth = computeUsedBreadthOfSpecifiedLength(direction, trackLength);
-        // FIXME: We should ASSERT that computedBreadth cannot return infinity but it's currently
-        // possible. See https://bugs.webkit.org/show_bug.cgi?id=107053
+        ASSERT(computedBreadth != infinity);
         return computedBreadth;
     }
 
     ASSERT(trackLength.isMinContent() || trackLength.isMaxContent());
     return infinity;
 }
 
 LayoutUnit RenderGrid::computeUsedBreadthOfSpecifiedLength(TrackSizingDirection direction, const Length& trackLength) const
 {
     // FIXME: We still need to support calc() here (https://webkit.org/b/103761).
@@ skipping 682 matching lines @@
     if (isOutOfFlowPositioned())
         return "RenderGrid (positioned)";
     if (isAnonymous())
         return "RenderGrid (generated)";
     if (isRelPositioned())
         return "RenderGrid (relative positioned)";
     return "RenderGrid";
 }
 
 } // namespace WebCore