Add missing build dependency

Add //ui/base/mojom as a dependency for //third_party/blink/public/mojom:mojom_core as LocalMainFrameHost depends on ui.mojom.WindowOpenDisposition as it's a parameter for LocalMainFrameHost::ShowCreatedWindow.

TBR=danakj@chromium.org
R=​oksamyt@chromium.org

Change-Id: Iaed399ab440c17d4607b778fab7b65fec296a676
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2506173
Commit-Queue: Alexander Timin <altimin@chromium.org>
Commit-Queue: Oksana Zhuravlova <oksamyt@chromium.org>
Auto-Submit: Alexander Timin <altimin@chromium.org>
Reviewed-by: Oksana Zhuravlova <oksamyt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821984}

third_party/blink/public/mojom/BUILD.gn

@@ -842,6 +842,7 @@ mojom("mojom_core") {
     "//services/service_manager/public/mojom",
     "//skia/public/mojom",
     "//third_party/blink/public/mojom/service_worker:storage",
+    "//ui/base/mojom",
     "//ui/gfx/geometry/mojom",
     "//ui/gfx/range/mojom",
     "//url/mojom:url_mojom_gurl",