[GN] Add support for generated proguard configs in android_apk

BUG=669961

Review-Url: https://codereview.chromium.org/2541763003
Cr-Original-Commit-Position: refs/heads/master@{#435460}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 6130422db2a8ff2a08ab0cd2b19d861825c900ae

config/android/rules.gni

@@ -1833,9 +1833,13 @@ if (enable_java_templates) {
         forward_variables_from(invoker,
                                [
                                  "alternative_android_sdk_jar",
+                                 "deps",
                                  "proguard_jar_path",
                                ])
-        deps = [
+        if (!defined(deps)) {
+          deps = []
+        }
+        deps += [
           ":$build_config_target",
           ":$java_target",
           ":$process_resources_target",