android: Allow bundle output path to be specified.

Defaults to "$root_build_dir/apks/" if base_bundle_path is not
specified.

Bug: 863113
Change-Id: Ia41ab38bce589ea95b462ec0ebf705c17ebd91a9
Reviewed-on: https://chromium-review.googlesource.com/1136987
Commit-Queue: Ben Mason <benmason@chromium.org>
Reviewed-by: David Turner <digit@chromium.org>
Reviewed-by: agrieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575295}

build/config/android/rules.gni

@@ -3429,6 +3429,13 @@ if (enable_java_templates) {
   #      the same content in its base module, though in a slightly different
   #      format.
   #
+  #    bundle_base_path: Optional. If set, the bundle will be output to this
+  #      directory. Defaults to "$root_build_dir/apks".
+  #
+  #    bundle_name: Optional. If set, the bundle will be output to the
+  #      filename "${bundle_name}.aab". Also, if generate_apks is true
+  #      "${bundle_name}.apks" will be used. Defaults to "${target_name}".
+  #
   #    extra_modules: Optional list of scopes, one per extra module used by
   #      this bundle. Each scope must have a 'name' field that specifies the
   #      module name (which cannot be 'base', since this is reserved for the
@@ -3531,7 +3538,12 @@ if (enable_java_templates) {
       _bundle_name = invoker.bundle_name
     }
 
-    _bundle_path = "$target_gen_dir/$_bundle_name.aab"
+    _bundle_base_path = "$root_build_dir/apks"
+    if (defined(invoker.bundle_base_path)) {
+      _bundle_base_path = invoker.bundle_base_path
+    }
+
+    _bundle_path = "$_bundle_base_path/$_bundle_name.aab"
     _rebased_bundle_path = rebase_path(_bundle_path, root_build_dir)
 
     _sign_bundle = defined(invoker.sign_bundle) && invoker.sign_bundle
@@ -3612,7 +3624,7 @@ if (enable_java_templates) {
       _android_aapt2_path = android_sdk_tools_bundle_aapt2
 
       _bundle_apks_target = "${target_name}_apks"
-      _bundle_apks_path = "$target_gen_dir/$_bundle_name.apks"
+      _bundle_apks_path = "$_bundle_base_path/$_bundle_name.apks"
 
       # NOTE: Keep this consistent with the imports of app_bundle_to_apks.py
       #       note that resource_utils.py imports build_utils.py