Update scroll-padding initial values in wpt tests.

There was a conflict in the scroll snap spec for the initial values of
scroll-padding-top/bottom/left/right[1]. Some of the initial values were
auto, while others were 0px. Now the conflict has been resolved with
all the initial values set to auto[2], we should update the wpt test to
reflect that.

The current implementation in Blink already reflects the updated spec,
so this patch also removes the expectations that were simply for the
failures.
[1] https://github.com/w3c/csswg-drafts/issues/3189
[2]
https://drafts.csswg.org/css-scroll-snap-1/#propdef-scroll-padding-top

Bug: 891954
Change-Id: Ib9c2280590091be27127abeee0a611b687cd37a2
Reviewed-on: https://chromium-review.googlesource.com/c/1299605Reviewed-by: Eric Willigers <ericwilligers@chromium.org>
Commit-Queue: Sandra Sun <sunyunjia@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602929}

third_party/WebKit/LayoutTests/external/wpt/css/css-scroll-snap/inheritance-expected.txt

-This is a testharness.js-based test.
-PASS Property scroll-margin-block-end has initial value 0px
-PASS Property scroll-margin-block-end does not inherit
-PASS Property scroll-margin-block-start has initial value 0px
-PASS Property scroll-margin-block-start does not inherit
-PASS Property scroll-margin-bottom has initial value 0px
-PASS Property scroll-margin-bottom does not inherit
-PASS Property scroll-margin-inline-end has initial value 0px
-PASS Property scroll-margin-inline-end does not inherit
-PASS Property scroll-margin-inline-start has initial value 0px
-PASS Property scroll-margin-inline-start does not inherit
-PASS Property scroll-margin-left has initial value 0px
-PASS Property scroll-margin-left does not inherit
-PASS Property scroll-margin-right has initial value 0px
-PASS Property scroll-margin-right does not inherit
-PASS Property scroll-margin-top has initial value 0px
-PASS Property scroll-margin-top does not inherit
-PASS Property scroll-padding-block-end has initial value auto
-PASS Property scroll-padding-block-end does not inherit
-PASS Property scroll-padding-block-start has initial value auto
-PASS Property scroll-padding-block-start does not inherit
-FAIL Property scroll-padding-bottom has initial value 0px assert_equals: expected "0px" but got "auto"
-PASS Property scroll-padding-bottom does not inherit
-PASS Property scroll-padding-inline-end has initial value auto
-PASS Property scroll-padding-inline-end does not inherit
-PASS Property scroll-padding-inline-start has initial value auto
-PASS Property scroll-padding-inline-start does not inherit
-FAIL Property scroll-padding-left has initial value 0px assert_equals: expected "0px" but got "auto"
-PASS Property scroll-padding-left does not inherit
-FAIL Property scroll-padding-right has initial value 0px assert_equals: expected "0px" but got "auto"
-PASS Property scroll-padding-right does not inherit
-FAIL Property scroll-padding-top has initial value 0px assert_equals: expected "0px" but got "auto"
-PASS Property scroll-padding-top does not inherit
-PASS Property scroll-snap-align has initial value none
-PASS Property scroll-snap-align does not inherit
-PASS Property scroll-snap-stop has initial value normal
-PASS Property scroll-snap-stop does not inherit
-PASS Property scroll-snap-type has initial value none
-PASS Property scroll-snap-type does not inherit
-Harness: the test ran to completion.
-

third_party/WebKit/LayoutTests/external/wpt/css/css-scroll-snap/inheritance.html

@@ -25,12 +25,12 @@ assert_not_inherited('scroll-margin-right', '0px', '10px');
 assert_not_inherited('scroll-margin-top', '0px', '10px');
 assert_not_inherited('scroll-padding-block-end', 'auto', '10px');
 assert_not_inherited('scroll-padding-block-start', 'auto', '10px');
-assert_not_inherited('scroll-padding-bottom', '0px', '10px');
+assert_not_inherited('scroll-padding-bottom', 'auto', '10px');
 assert_not_inherited('scroll-padding-inline-end', 'auto', '10px');
 assert_not_inherited('scroll-padding-inline-start', 'auto', '10px');
-assert_not_inherited('scroll-padding-left', '0px', '10px');
-assert_not_inherited('scroll-padding-right', '0px', '10px');
-assert_not_inherited('scroll-padding-top', '0px', '10px');
+assert_not_inherited('scroll-padding-left', 'auto', '10px');
+assert_not_inherited('scroll-padding-right', 'auto', '10px');
+assert_not_inherited('scroll-padding-top', 'auto', '10px');
 assert_not_inherited('scroll-snap-align', 'none', 'start end');
 assert_not_inherited('scroll-snap-stop', 'normal', 'always');
 assert_not_inherited('scroll-snap-type', 'none', 'inline proximity');