Change the default appearance of <progress> and <meter> to 'auto'

This doesn't change rendering behavior, but changes
|getComputedStyle(element)['appearance']| results. The new behavior
matches to Firefox.

Bug: 965432
Change-Id: Id354dd63f0034f2863f594aaf653c624123979b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2389880
Commit-Queue: Yoshifumi Inoue <yosin@chromium.org>
Auto-Submit: Kent Tamura <tkent@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804127}

third_party/blink/renderer/core/html/resources/html.css

@@ -890,7 +890,7 @@ output {
 /* meter */
 
 meter {
-    -webkit-appearance: meter; /* AutoAppearanceFor() should match to this. */
+    appearance: auto;
     box-sizing: border-box;
     display: inline-block;
     height: 1em;
@@ -900,7 +900,7 @@ meter {
 }
 
 meter::-webkit-meter-inner-element {
-    -webkit-appearance: inherit; /* AutoAppearanceFor() should match to this. */
+    appearance: inherit;
     box-sizing: inherit;
     display: none;
     -webkit-user-modify: read-only !important;
@@ -948,7 +948,7 @@ meter::-webkit-meter-even-less-good-value {
 /* progress */
 
 progress {
-    -webkit-appearance: progress-bar; /* AutoAppearanceFor() should match to this. */
+    appearance: auto;
     box-sizing: border-box;
     display: inline-block;
     height: 1em;

third_party/blink/web_tests/external/wpt/html/rendering/widgets/appearance/default-styles-expected.txt

@@ -26,8 +26,8 @@ FAIL <select multiple=""> assert_equals: -webkit-appearance expected "auto" but
 FAIL <select size="2"> assert_equals: -webkit-appearance expected "auto" but got "listbox"
 FAIL <button> assert_equals: -webkit-appearance expected "auto" but got "button"
 FAIL <textarea> assert_equals: -webkit-appearance expected "auto" but got "textarea"
-FAIL <meter> assert_equals: -webkit-appearance expected "auto" but got "meter"
-FAIL <progress> assert_equals: -webkit-appearance expected "auto" but got "progress-bar"
+PASS <meter>
+PASS <progress>
 PASS <input type="hidden">
 PASS <input type="HIDDEN">
 PASS <input type="file">