android: Introduce a ui::PlatformWindow implementation for android.

components/view_manager/native_viewport/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/ui.gni")
 
 source_set("native_viewport") {
   sources = [
     "onscreen_context_provider.cc",
     "onscreen_context_provider.h",
     "platform_viewport.h",
-    "platform_viewport_android.cc",
-    "platform_viewport_android.h",
+    "platform_viewport_common.cc",
     "platform_viewport_headless.cc",
     "platform_viewport_headless.h",
     "platform_viewport_stub.cc",
-    "platform_viewport_win.cc",
-    "platform_viewport_x11.cc",
   ]
 
   if (!is_ios) {
     sources -= [ "platform_viewport_stub.cc" ]
   }
 
   deps = [
     "//base",
     "//components/view_manager/gles2",
     "//components/view_manager/public/interfaces",
     "//gpu/command_buffer/service",
     "//mojo/application/public/cpp",
     "//mojo/common:tracing_impl",
     "//mojo/converters/geometry",
     "//mojo/converters/input_events",
     "//ui/events",
     "//ui/events/platform",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gl",
     "//ui/mojo/geometry:interfaces",
-    "//ui/platform_window",
+    "//ui/platform_window:platform_impls",
   ]
-
-  if (is_android) {
-    deps += [ "//components/view_manager:jni_headers" ]
-  }
-
-  if (use_x11) {
-    deps += [ "//ui/platform_window/x11" ]
-  } else {
-    sources -= [ "platform_viewport_x11.cc" ]
-  }
-
-  if (is_win) {
-    deps += [ "//ui/platform_window/win" ]
-  }
 }