WebUI cleanup: Move cr.ui.BubbleButton to the last place it is used.

Since it is only used in one place, there is no reason for this
(deprecated) UI component to be in shared WebUI code.

As a result of this CL bubble_button.js/css is no longer part of the
build in non-CrOS, and in CrOS is inlined within arc_suport/main.html
as a result of the |flattenhtml| usage on that file.

Bug: None
Change-Id: I9838bc4a9a6b71370fbc212d1e189311045b0813
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2643091
Auto-Submit: dpapad <dpapad@chromium.org>
Commit-Queue: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Cr-Commit-Position: refs/heads/master@{#846200}

chrome/browser/resources/chromeos/arc_support/main.html

@@ -4,7 +4,7 @@
   <title i18n-content="appWindow"></title>
   <link rel="stylesheet" href="chrome://resources/css/roboto.css">
   <link rel="stylesheet" href="chrome://resources/css/bubble.css">
-  <link rel="stylesheet" href="chrome://resources/css/bubble_button.css">
+  <link rel="stylesheet" href="bubble_button.css">
   <link rel="stylesheet" href="chrome://resources/css/overlay.css">
   <link rel="stylesheet" href="controlled_indicator.css">
   <link rel="stylesheet" href="main.css">
@@ -21,7 +21,7 @@
   <script src="chrome://resources/js/event_tracker.js"></script>
   <script src="chrome://resources/js/cr/ui.js"></script>
   <script src="chrome://resources/js/cr/ui/bubble.js"></script>
-  <script src="chrome://resources/js/cr/ui/bubble_button.js"></script>
+  <script src="bubble_button.js"></script>
   <script src="chrome://resources/js/cr/ui/overlay.js"></script>
   <script src="chrome://resources/js/cr/ui/focus_manager.js"></script>
   <script type="module" src="main.js"></script>

ui/webui/resources/css/BUILD.gn

@@ -26,7 +26,6 @@ preprocess_if_expr("preprocess_src") {
     "action_link.css",
     "apps/common.css",
     "apps/topbutton_bar.css",
-    "bubble_button.css",
     "bubble.css",
     "butter_bar.css",
     "chrome_shared.css",

ui/webui/resources/js/cr/ui/BUILD.gn

@@ -37,7 +37,6 @@ preprocess_if_expr("preprocess_src") {
   out_manifest = "$target_gen_dir/$preprocess_src_manifest"
   in_files = [
     "array_data_model.js",
-    "bubble_button.js",
     "bubble.js",
     "command.js",
     "context_menu_handler.js",