mediaview: Add a typemap for arc::mojom::ChangeType.

Also fixes storage/browser/BUILD.gn, which is needed to pass gn gen --check.

BUG=chromium:698623
TEST=gn gen --check

Review-Url: https://codereview.chromium.org/2727113002
Cr-Commit-Position: refs/heads/master@{#455662}
diff --git a/components/arc/DEPS b/components/arc/DEPS
index b0c29d21..25269a0 100644
--- a/components/arc/DEPS
+++ b/components/arc/DEPS
@@ -7,6 +7,7 @@
   "+components/signin/core/account_id",
   "+components/user_manager",
   "+mojo",
+  "+storage/browser/fileapi",
   "+third_party/re2",
   "+third_party/skia",
   "+ui/gfx/geometry/rect.h",