Add BubbleManager to manage bubbles and ChromeBubbleManager for events.

components/bubble/BUILD.gn

Index: components/bubble/BUILD.gn
diff --git a/ui/platform_window/stub/BUILD.gn b/components/bubble/BUILD.gn
similarity index 51%
copy from ui/platform_window/stub/BUILD.gn
copy to components/bubble/BUILD.gn
index 4a3a42ce607e90f0ae5e45b72c9e468432194d1c..0fb72a4bb123eb1c29254c79dab88e9478a871f6 100644
--- a/ui/platform_window/stub/BUILD.gn
+++ b/components/bubble/BUILD.gn
@@ -2,19 +2,18 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-component("stub") {
-  output_name = "stub_window"
+static_library("bubble") {
+  sources = [
+    "bubble_controller.cc",
+    "bubble_controller.h",
+    "bubble_delegate.cc",
+    "bubble_delegate.h",
+    "bubble_manager.cc",
+    "bubble_manager.h",
+    "bubble_ui.h",
+  ]
 
   deps = [
     "//ui/gfx",
-    "//ui/platform_window",
-  ]
-
-  defines = [ "STUB_WINDOW_IMPLEMENTATION" ]
-
-  sources = [
-    "stub_window.cc",
-    "stub_window.h",
-    "stub_window_export.h",
   ]
 }