Enable gesture tap highlight tests on mac

These were disabled in https://codereview.chromium.org/34353004 but
now run. The setting, multiTargetTapNotificationEnabled, is enabled on
all platforms.

This patch unskips the gesture tap highlight tests on mac and updates
their expectations.

Bug: 857501
Change-Id: I4bb6c91cd5b75d3fe30420759073f404a62d896f
Cq-Include-Trybots: luci.chromium.try:linux-blink-gen-property-trees;luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Reviewed-on: https://chromium-review.googlesource.com/1121786Reviewed-by: David Bokan <bokan@chromium.org>
Commit-Queue: Philip Rogers <pdr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#572293}

third_party/WebKit/LayoutTests/NeverFixTests

@@ -88,9 +88,6 @@ fast/harness/results.html [ WontFix ]
 [ Mac ] virtual/user-activation-v2/fast/events/menu-key-context-menu-reveal-focus.html [ WontFix ]
 [ Mac ] virtual/user-activation-v2/fast/events/menu-key-context-menu.html [ WontFix ]
 
-# Link Highlighting is only supported on Windows and Linux
-[ Mac ] compositing/gestures [ WontFix ]
-
 # These tests are specific to Linux.
 [ Mac Win ] editing/input/linux_ltr_composition_underline.html [ WontFix ]
 [ Mac Win ] editing/input/linux_rtl_composition_underline.html [ WontFix ]