Add a snapshot of flutter/engine/src/build to our sdk

build/android/adb_gdb_android_webview_shell

Index: build/android/adb_gdb_android_webview_shell
diff --git a/build/android/adb_gdb_android_webview_shell b/build/android/adb_gdb_android_webview_shell
new file mode 100755
index 0000000000000000000000000000000000000000..f685fda77c5e3c7bdd4b9345d2c15f5ddb6d342e
--- /dev/null
+++ b/build/android/adb_gdb_android_webview_shell
@@ -0,0 +1,16 @@
+#!/bin/bash
+#
+# Copyright (c) 2013 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.
+#
+# Attach to or start a ContentShell process and debug it.
+# See --help for details.
+#
+PROGDIR=$(dirname "$0")
+export ADB_GDB_PROGNAME=$(basename "$0")
+export ADB_GDB_ACTIVITY=.AwShellActivity
+"$PROGDIR"/adb_gdb \
+    --program-name=AwShellApplication \
+    --package-name=org.chromium.android_webview.shell \
+    "$@"