[LayoutNG] Rebaseline fast/dom/HTMLAreaElement/area-download.html

After getting an NG-specific rebaseline [1] due to whitespace only
difference, the layout tests's generic baseline was changed [2],
cause failure on NG bot.

This patch rebaselines it to make it pass again.

[1] https://crrev.com/c/942646
[2] https://crrev.com/c/992322

Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng
Change-Id: Ib81eb9ce05cc36c11496be895434248aa9318c19
Reviewed-on: https://chromium-review.googlesource.com/1151958
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Commit-Queue: Emil A Eklund <eae@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578454}

third_party/WebKit/LayoutTests/FlagExpectations/enable-blink-features=LayoutNG

@@ -518,7 +518,6 @@ crbug.com/591099 fast/css/outline-narrowLine.html [ Failure ]
 crbug.com/591099 fast/css/transform-inline-style-remove.html [ Failure ]
 crbug.com/591099 fast/css3-text/css3-text-decoration/text-underline-position/text-underline-position-auto.html [ Failure ]
 crbug.com/591099 fast/css3-text/css3-text-decoration/text-underline-position/text-underline-position-under.html [ Failure ]
-crbug.com/591099 fast/dom/HTMLAreaElement/area-download.html [ Failure ]
 crbug.com/591099 fast/dom/nodesFromRect/nodesFromRect-basic.html [ Failure ]
 crbug.com/591099 fast/dynamic/first-letter-after-list-marker.html [ Failure ]
 crbug.com/591099 fast/encoding/utf-16-big-endian.html [ Failure ]

third_party/WebKit/LayoutTests/flag-specific/enable-blink-features=LayoutNG/fast/dom/HTMLAreaElement/area-download-expected.txt

-Downloading URL with suggested filename "foo"
+Download started