Add GN template for android_assets(). Use it in content_shell_apk.

gin/BUILD.gn

Index: gin/BUILD.gn
diff --git a/gin/BUILD.gn b/gin/BUILD.gn
index 0b270c5894aa24aa21c286282d74b3adc8941d1f..590eed817e54f649daecf2f3046ec2b1677669a8 100644
--- a/gin/BUILD.gn
+++ b/gin/BUILD.gn
@@ -5,6 +5,10 @@
 import("//build_overrides/v8.gni")
 import("//testing/test.gni")
 
+if (is_android) {
+  import("//build/config/android/rules.gni")
+}
+
 component("gin") {
   sources = [
     "arguments.cc",
@@ -93,6 +97,21 @@ component("gin") {
   configs += [ "//v8:external_startup_data" ]
 }
 
+if (is_android) {
+  android_assets("v8_snapshot_assets") {
+    if (v8_use_external_startup_data) {
+      deps = [
+        "//v8",
+      ]
+      sources = [
+        "$root_out_dir/natives_blob.bin",
+        "$root_out_dir/snapshot_blob.bin",
+      ]
+    }
+    enable_compression = false
+  }
+}
+
 if (v8_use_external_startup_data) {
   action("gin_v8_snapshot_fingerprint") {
     script = "//gin/fingerprint/fingerprint_v8_snapshot.py"