Download and copy shell binary on Android as well as Linux.

mojo/public/tools/BUILD.gn

Index: mojo/public/tools/BUILD.gn
diff --git a/mojo/public/tools/BUILD.gn b/mojo/public/tools/BUILD.gn
index 12cca6df2e1e26cd123eb6ac3e985f76ce79c4e7..103c25973a9eb195a6ad5e9c69ae1db8adb34361 100644
--- a/mojo/public/tools/BUILD.gn
+++ b/mojo/public/tools/BUILD.gn
@@ -10,11 +10,20 @@ if (use_prebuilt_mojo_shell) {
     if (is_win) {
       filename += ".exe"
     }
+    if (is_android) {
+      filename = "MojoShell.apk"
+    }
     sources = [
       "prebuilt/$filename",
     ]
-    outputs = [
-      "$root_out_dir/$filename",
-    ]
+    if (is_android) {
+      outputs = [
+        "$root_out_dir/apks/$filename",
+      ]
+    } else {
+      outputs = [
+        "$root_out_dir/$filename",
+      ]
+    }
   }
 }