Output Proguard options for also overlay layouts.

Change-Id: I7bfac476247bd7b532510e295cb1a3e61e9af88b
diff --git a/tools/aapt/Resource.cpp b/tools/aapt/Resource.cpp
index 730bd71..b4ac929 100644
--- a/tools/aapt/Resource.cpp
+++ b/tools/aapt/Resource.cpp
@@ -2194,6 +2194,11 @@
             }
         }
     }
+    // Handle the overlays
+    sp<AaptAssets> overlay = assets->getOverlay();
+    if (overlay.get()) {
+        return writeProguardForLayouts(keep, overlay);
+    }
     return NO_ERROR;
 }