Use fuzzy matching in composited-filters-under-opacity.html

https://crrev.com/1665715 changed the reference for
composited-filters-under-opacity.html in a way that makes the test not
cover the original goals (see: http://crrev.com/653319). This patch
reverts https://crrev.com/1665715 and instead adds fuzzy matching, as
being off by 1 is fine for this test.

Change-Id: I39baa73181fb4ab74243044f1b1e130e6137bf34
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/8145500
Reviewed-by: Keren Zhu <kerenzhu@chromium.org>
Auto-Submit: Philip Rogers <pdr@chromium.org>
Commit-Queue: Keren Zhu <kerenzhu@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1669217}

Author: progers

css/css-color/composited-filters-under-opacity-ref.html

@@ -2,7 +2,6 @@
 <style>
 div {
   position: absolute;
-  will-change: opacity;
 }
 .content {
   width: 100px;
@@ -12,7 +11,7 @@
 }
 </style>
 Below should be a light blue square in uniform color.
-<div style="opacity: 0.5">
+<div style="opacity: 0.5; will-change: opacity;">
   <div class="content" style="left: 0"></div>
   <div class="content" style="left: 50px"></div>
 </div>

css/css-color/composited-filters-under-opacity.html

@@ -1,5 +1,6 @@
 <link rel="help" href="http://www.w3.org/TR/css3-color/#transparency">
 <link rel="match" href="composited-filters-under-opacity-ref.html">
+<meta name="fuzzy" content="maxDifference=0-1;totalPixels=0-22500">
 <style>
 div {
   position: absolute;