Ensure android_manifest_dep is always used in place of deps

Main motivation is to be able to write .build_config files quickly, so
that they can be used for generating build.gradle files for Android
Studio without first needing to build a bunch of native libraries.

BUG=620034

Review-Url: https://codereview.chromium.org/2088743003
Cr-Commit-Position: refs/heads/master@{#401520}
diff --git a/testing/test.gni b/testing/test.gni
index b93ef87..80033ff 100644
--- a/testing/test.gni
+++ b/testing/test.gni
@@ -161,6 +161,7 @@
       _apk_target = "${target_name}_apk"
       _apk_specific_vars = [
         "android_manifest",
+        "android_manifest_dep",
         "enable_multidex",
         "proguard_configs",
         "proguard_enabled",