Rebaseline window-resize-background-image-fixed-scrolling-contents.html on Mac

TBR=wangxianzhu@chromium.org

Bug: 1107272
Change-Id: Ic18a96b452e56d97fa2921d8844ca2364aeddcdf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2306912Reviewed-by: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789819}

third_party/blink/web_tests/platform/mac/paint/invalidation/window-resize/window-resize-background-image-fixed-scrolling-contents-expected.txt

@@ -6,7 +6,7 @@
       "contentsOpaque": true,
       "backgroundColor": "#FFFFFF",
       "invalidations": [
-        [0, 0, 600, 250]
+        [0, 0, 585, 250]
       ]
     },
     {
@@ -52,7 +52,7 @@
       "contentsOpaque": true,
       "backgroundColor": "#FFFFFF",
       "invalidations": [
-        [0, 0, 400, 600]
+        [0, 0, 385, 600]
       ]
     },
     {
@@ -75,7 +75,7 @@
       "contentsOpaque": true,
       "backgroundColor": "#FFFFFF",
       "invalidations": [
-        [0, 0, 800, 600]
+        [0, 0, 785, 600]
       ]
     },
     {