Reland "[blinkpy] Re-enable four css-background/ tests that need fuzzy reftest"

This reverts commit 86af9c78, thus
relanding 8970a3d2.

Bug: 997202,1156287
Change-Id: I73b7f8eb8ba109cc71eb8d63ee58ec32b16f76b8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2578169Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Stephen McGruer <smcgruer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#834769}

third_party/blink/web_tests/TestExpectations

@@ -215,12 +215,6 @@ crbug.com/1093466 virtual/portals/http/tests/inspector-protocol/portals/* [ Pass
 crbug.com/1093466 virtual/portals/http/tests/portals/* [ Pass ]
 crbug.com/1093466 virtual/portals/wpt_internal/portals/* [ Pass ]
 
-# Subpixel differences
-crbug.com/997202 external/wpt/css/css-backgrounds/background-attachment-local/attachment-local-clipping-color-5.html [ Failure ]
-crbug.com/997202 external/wpt/css/css-backgrounds/background-attachment-local/attachment-local-clipping-image-5.html [ Failure ]
-crbug.com/997202 external/wpt/css/css-backgrounds/border-radius-clip-001.html [ Failure ]
-crbug.com/997202 external/wpt/css/css-backgrounds/border-radius-clip-002.htm [ Failure ]
-
 crbug.com/807395 fast/multicol/mixed-opacity-test.html [ Failure ]
 
 ########## Ref tests can't be rebaselined ##########
@@ -3281,6 +3275,8 @@ crbug.com/697971 [ Mac10.12 ] virtual/text-antialias/selection/flexbox-selection
 # [composite-bgcolor-animation]
 crbug.com/1148369 virtual/composite-bgcolor-animation/external/wpt/css/css-backgrounds/border-bottom-left-radius-010.xht [ Failure ]
 crbug.com/1148369 virtual/composite-bgcolor-animation/external/wpt/css/css-backgrounds/border-bottom-right-radius-010.xht [ Failure ]
+crbug.com/1148369 virtual/composite-bgcolor-animation/external/wpt/css/css-backgrounds/border-radius-clip-001.html [ Failure ]
+crbug.com/1148369 virtual/composite-bgcolor-animation/external/wpt/css/css-backgrounds/border-radius-clip-002.htm [ Failure ]
 crbug.com/1148369 virtual/composite-bgcolor-animation/external/wpt/css/css-backgrounds/border-top-left-radius-010.xht [ Failure ]
 crbug.com/1148369 virtual/composite-bgcolor-animation/external/wpt/css/css-backgrounds/border-top-right-radius-010.xht [ Failure ]
 

third_party/blink/web_tests/external/wpt/css/css-backgrounds/background-attachment-local/attachment-local-clipping-color-5.html

@@ -2,6 +2,7 @@
 <title>CSS Test: background-{attachment: local; clip: padding-box; color}; border-radius</title>
 <link rel="match" href="attachment-local-clipping-color-4-ref.html" />
 <meta name="flags" content="dom" />
+<meta name=fuzzy content="0-10;0-160">
 <link rel="author" title="Simon Sapin" href="http://exyr.org/about/" />
 <link rel="help" href="http://www.w3.org/TR/css3-background/#the-background-attachment" />
 <style>

third_party/blink/web_tests/external/wpt/css/css-backgrounds/background-attachment-local/attachment-local-clipping-image-5.html

@@ -2,6 +2,7 @@
 <title>CSS Test: background-{attachment: local; clip: padding-box; image}; border-radius</title>
 <link rel="match" href="attachment-local-clipping-image-4-ref.html" />
 <meta name="flags" content="dom" />
+<meta name=fuzzy content="0-10;0-300">
 <link rel="author" title="Simon Sapin" href="http://exyr.org/about/" />
 <link rel="help" href="http://www.w3.org/TR/css3-background/#the-background-attachment" />
 <style>

third_party/blink/web_tests/external/wpt/css/css-backgrounds/border-radius-clip-001.html

@@ -12,6 +12,8 @@
 
   <meta name="assert" content="Test passes if a box with border-radius that clips its content to a box edge clips to the border-radius curve in the corners.">
 
+  <meta name="fuzzy" content="0-1;0-1000">
+
   <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
   <style>
   body > div { float: left; }

third_party/blink/web_tests/external/wpt/css/css-backgrounds/border-radius-clip-002.htm

@@ -7,6 +7,7 @@
         <link rel="match" href="reference/border-radius-clip-002-ref.htm">
         <link rel="help" href="https://www.w3.org/TR/css-backgrounds-3/#corner-clipping">
         <meta name="assert" content="Background is clipped to the curve of the content-box when 'background-clip: content-box'">
+        <meta name=fuzzy content="0-70;0-50">
         <style type="text/css">
             #test-base
             {