Refactors keyboard related code so mash can use a keyboard

ash/BUILD.gn

Index: ash/BUILD.gn
diff --git a/ash/BUILD.gn b/ash/BUILD.gn
index e6ecc7244e83b589c5677f78cc2bbbf194de6501..69fe0f09582acb9ac9183ebba5ee9c16426fc884 100644
--- a/ash/BUILD.gn
+++ b/ash/BUILD.gn
@@ -16,9 +16,16 @@ gypi_values = exec_script("//build/gypi_to_gn.py",
 
 component("ash") {
   sources = gypi_values.ash_sources
+  sources += [
+    "keyboard/keyboard_ui_mus.cc",
+    "keyboard/keyboard_ui_mus.h",
+  ]
 
   configs += [ "//build/config:precompiled_headers" ]
-  defines = [ "ASH_IMPLEMENTATION" ]
+  defines = [
+    "ASH_IMPLEMENTATION",
+    "MOJO_SHELL_CLIENT",
+  ]
 
   public_deps = [
     "//ash/resources",
@@ -35,6 +42,8 @@ component("ash") {
     "//components/user_manager",
     "//components/wallpaper",
     "//media",
+    "//mojo/public/c/system:for_component",
+    "//mojo/shell/public/cpp",
     "//net",
     "//skia",
     "//third_party/icu",
@@ -52,6 +61,7 @@ component("ash") {
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/keyboard",
+    "//ui/keyboard:mojom",
     "//ui/message_center",
     "//ui/platform_window/stub",
     "//ui/resources",