views: Enable toolkit_views on Cast Fuchsia

This is already in use as evidenced by the build failures
in https://chromium-review.googlesource.com/c/chromium/src/+/1918654.

Enable it so the //ui/views build file can verify toolkit_views=true,
which will help diagnose invalid dependencies on platforms that don't
intend to use views (such as Chromecast Android).

Bug: 1021770

Change-Id: Iefef6bf25f26d50ac6e871bc17c96b1ba74b3c97
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1946850
Commit-Queue: Michael Spang <spang@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721164}

build/config/ui.gni

@@ -32,7 +32,7 @@ declare_args() {
 
 declare_args() {
   # True means the UI is built using the "views" framework.
-  toolkit_views = (is_mac || is_win || is_chromeos || use_aura) && !is_fuchsia
+  toolkit_views = is_mac || is_win || is_linux || (is_fuchsia && is_chromecast)
 
   # Whether we should use glib, a low level C utility library.
   use_glib = is_linux && !use_ozone

components/BUILD.gn

@@ -8,6 +8,7 @@ import("//build/config/ui.gni")
 import("//components/nacl/features.gni")
 import("//components/safe_browsing/buildflags.gni")
 import("//components/ui_devtools/devtools.gni")
+import("//extensions/buildflags/buildflags.gni")
 import("//media/media_options.gni")
 import("//ppapi/buildflags/buildflags.gni")
 import("//printing/buildflags/buildflags.gni")
@@ -180,10 +181,13 @@ test("components_unittests") {
     deps += [
       "//components/media_message_center:unit_tests",
       "//components/ui_devtools:unit_tests",
-      "//components/ui_devtools/views:unit_tests",
     ]
   }
 
+  if (toolkit_views && enable_extensions) {
+    deps += [ "//components/ui_devtools/views:unit_tests" ]
+  }
+
   if (use_viz_devtools) {
     deps += [ "//components/ui_devtools/viz:unit_tests" ]
   }