bug 1246772 - work around x87 floating point truncation issues in gecko r=dholbert

test_value_storage.html needs floating point numbers to round trip through css
parsing and serialization, but floating point isn't exact so we should be
careful what numbers we test.  It turns out the value 0.9 the test was using is
close to the border between 229 and 230 when converted to an 8 bit int, but 0.8
is safer so change to that since the test doesn't depend on the value.  Note
that this does not fix the issue that numbers don't always round trip, but only
wall papers over it by changing the test.

layout/style/test/property_database.js

@@ -665,7 +665,7 @@ if (IsCSSPropertyPrefEnabled("layout.css.prefixes.webkit")) {
     "-webkit-gradient(linear, 1 2, 3 4, color-stop(0, rgb(1,2,3)))",
     "-webkit-gradient(linear, 1 2, 3 4, color-stop(0, #00ff00))",
     "-webkit-gradient(linear, 1 2, 3 4, color-stop(0, #00f))",
-    "-webkit-gradient(linear, 1 2, 3 4, color-stop(0, hsla(240, 30%, 50%, 0.9)))",
+    "-webkit-gradient(linear, 1 2, 3 4, color-stop(0, hsla(240, 30%, 50%, 0.8)))",
     "-webkit-gradient(linear, 1 2, 3 4, color-stop(0, rgba(255, 230, 10, 0.5)))",
 
     // linear w/ multiple color stops: