Make unconstrained width assertions into warnings because we can hit them when we clamp really large widths. (Bug 525100) r=roc

gfx/src/thebes/crashtests/crashtests.list

@@ -1,4 +1,4 @@
 load 306902-1.xml
 load 383872-1.svg
-asserts(8) load 423110-1.xhtml
+load 423110-1.xhtml
 load 445711.html

layout/base/nsLayoutUtils.cpp

@@ -2191,8 +2191,10 @@ nsLayoutUtils::ComputeWidthDependentValue(
                  nscoord              aContainingBlockWidth,
                  const nsStyleCoord&  aCoord)
 {
-  NS_PRECONDITION(aContainingBlockWidth != NS_UNCONSTRAINEDSIZE,
-                  "unconstrained widths no longer supported");
+  NS_WARN_IF_FALSE(aContainingBlockWidth != NS_UNCONSTRAINEDSIZE,
+                   "have unconstrained width; this should only result from "
+                   "very large sizes, not attempts at intrinsic width "
+                   "calculation");
 
   if (eStyleUnit_Coord == aCoord.GetUnit()) {
     return aCoord.GetCoordValue();