Migrate `front_end/layer_viewer` to `devtools_entrypoint`

Bug: 1101738
Change-Id: I9572585fe67702098a5774870993c8da4cb55c17
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2328851
Commit-Queue: Jan Scheffler <[email protected]>
Reviewed-by: Jack Franklin <[email protected]>
diff --git a/front_end/BUILD.gn b/front_end/BUILD.gn
index fe3b7fa..55d4896 100644
--- a/front_end/BUILD.gn
+++ b/front_end/BUILD.gn
@@ -36,6 +36,7 @@
     "issues:bundle",
     "javascript_metadata:bundle",
     "js_main:bundle",
+    "layer_viewer:bundle",
     "mobile_throttling:bundle",
     "object_ui:bundle",
     "perf_ui:bundle",