Add to read |text_track_text_color| field to WebPreferences Mojom traits

crrev.com/c/2631705 removed the read of |text_track_text_color|. This CL
restore to read the varialble in WebPreferences StructTraits.

Bug: 1097943, 1166690
Change-Id: I1695551bc8eabe39bc8f129471a519af1ae42b98
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2631557Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Gyuyoung Kim <gyuyoung@igalia.com>
Cr-Commit-Position: refs/heads/master@{#844449}

third_party/blink/common/web_preferences/web_preferences_mojom_traits.cc

@@ -31,6 +31,7 @@ bool StructTraits<blink::mojom::WebPreferencesDataView,
       !data.ReadLazyImageFirstKFullyLoad(&out->lazy_image_first_k_fully_load) ||
       !data.ReadDefaultEncoding(&out->default_encoding) ||
       !data.ReadTextTrackBackgroundColor(&out->text_track_background_color) ||
+      !data.ReadTextTrackTextColor(&out->text_track_text_color) ||
       !data.ReadTextTrackTextSize(&out->text_track_text_size) ||
       !data.ReadTextTrackTextShadow(&out->text_track_text_shadow) ||
       !data.ReadTextTrackFontFamily(&out->text_track_font_family) ||