Disable rendering.desktop on win7.

This is failing consistently.

BUG=1059200
NOTRY=true
CC=sadrul@chromium.org,vmiura@chromium.org
TBR=crouleau@chromium.org

Change-Id: I59fddd72d46e8675f1db236528d4d2609567c301
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2090415Reviewed-by: Stephen Nusko <nuskos@chromium.org>
Commit-Queue: Stephen Nusko <nuskos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747642}

tools/perf/expectations.config

@@ -222,6 +222,7 @@ crbug.com/1017244 [ desktop ] rendering.desktop/youtube_2018 [ Skip ]
 crbug.com/1017244 [ desktop ] rendering.desktop/youtube_pinch_2018 [ Skip ]
 crbug.com/1044962 [ win ] rendering.desktop/camera_to_webgl [ Skip ]
 crbug.com/1053614 [ win ] rendering.desktop/filter_terrain_svg [ Skip ]
+crbug.com/1059200 [ win7 ] rendering.desktop/canvas_to_blob [ Skip ]
 
 # Benchmark: rendering.mobile
 crbug.com/785485 [ android-webview ] rendering.mobile/kevs_3d [ Skip ]