Add gn support for generating mojo_shell_apk

mojo/shell/BUILD.gn

Index: mojo/shell/BUILD.gn
diff --git a/mojo/shell/BUILD.gn b/mojo/shell/BUILD.gn
index 491dd17cb1aef8003a359dc57b0f69f067911c35..3fb1f456492e796dc693397f7a74dfb5f5f711c4 100644
--- a/mojo/shell/BUILD.gn
+++ b/mojo/shell/BUILD.gn
@@ -6,6 +6,11 @@ import("//build/config/ui.gni")
 import("//mojo/public/mojo.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 
+if (is_android) {
+  import("//build/config/android/config.gni")
+  import("//build/config/android/rules.gni")
+}
+
 if (!use_prebuilt_mojo_shell) {
 
 # GYP version: mojo/mojo.gyp:mojo_shell
@@ -98,6 +103,62 @@ source_set("lib") {
   }
 }
 
+if (is_android) {
+  generate_jni("jni_headers") {
+    sources = [
+      "android/apk/src/org/chromium/mojo_shell_apk/MojoMain.java",
+    ]
+    jni_package = "mojo"
+  }
+
+  android_library("java") {
+    deps = [
+      "//base:base_java",
+      "//net/android:net_java",
+    ]
+    java_files = [
+      "android/apk/src/org/chromium/mojo_shell_apk/MojoMain.java",
+      "android/apk/src/org/chromium/mojo_shell_apk/MojoShellActivity.java",
+      "android/apk/src/org/chromium/mojo_shell_apk/MojoShellApplication.java",
+    ]
+  }
+
+  android_resources("resources") {
+    resource_dirs = [ "android/apk/res" ]
+    custom_package = "org.chromium.mojo_shell_apk"
+  }
+
+  shared_library("libmojo_shell") {
+    deps = [
+      ":jni_headers",
+      ":lib",
+      "//ui/gl",
+    ]
+
+    sources = [
+      "android/library_loader.cc",
+      "android/mojo_main.cc",
+      "android/mojo_main.h",
+    ]
+  }
+
+  android_apk("mojo_shell_apk") {
+    deps = [
+      ":java",
+      ":libmojo_shell",
+      ":resources",
+      "//mojo/services/native_viewport:native_viewport_java",
+    ]
+
+    native_libs = [
+      "libmojo_shell.so"
+    ]
+
+    apk_name = "MojoShell"
+    android_manifest = "android/apk/AndroidManifest.xml"
+  }
+}
+
 mojom("app_child_process_bindings") {
   sources = [
     "app_child_process.mojom"