[test] Unskip layout tests after fixing bot.

BUG=chromium:498689
LOG=n
NOTRY=true
TBR=sergiyb@chromium.org

Review URL: https://codereview.chromium.org/1185623003

Cr-Commit-Position: refs/heads/master@{#29101}

tools/blink_tests/TestExpectations

@@ -3,7 +3,3 @@
 # Turn off Slimming Paint tests on linux.
 [ Linux ] virtual/slimmingpaint/ [ Skip ]
 
-crbug.com/498689 [ Linux ] virtual/display_list_2d_canvas/canvas/philip/tests/ [ Skip ]
-crbug.com/498689 [ Linux ] virtual/gpu/canvas/philip/tests/ [ Skip ]
-crbug.com/498689 [ Linux ] canvas/philip/tests/ [ Skip ]
-