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

components/view_manager/native_viewport/BUILD.gn

Index: components/view_manager/native_viewport/BUILD.gn
diff --git a/components/view_manager/native_viewport/BUILD.gn b/components/view_manager/native_viewport/BUILD.gn
index ae0014cbc4be741b4c313db41b473432d2b3bacd..350c16f6076c65d629b34f82c23696181f9b101b 100644
--- a/components/view_manager/native_viewport/BUILD.gn
+++ b/components/view_manager/native_viewport/BUILD.gn
@@ -9,13 +9,10 @@ source_set("native_viewport") {
     "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) {
@@ -37,20 +34,6 @@ source_set("native_viewport") {
     "//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" ]
-  }
 }