Reland "Enable maintain_prefix for function"

This reverts commit cf1e8d417680278fae15d4c66dc03e2031871f22.

Reland "Move desugared lib test method"

This reverts commit 06f3809eac0750754bf5d4a86b710417f406d107.

Change-Id: I8d2422029b1d1a6ea3beafedb500e66c7553cb0b
diff --git a/src/library_desugar/jdk11/desugar_jdk_libs_minimal.json b/src/library_desugar/jdk11/desugar_jdk_libs_minimal.json
index 73fa330..8064ed0 100644
--- a/src/library_desugar/jdk11/desugar_jdk_libs_minimal.json
+++ b/src/library_desugar/jdk11/desugar_jdk_libs_minimal.json
@@ -17,6 +17,7 @@
   "library_flags": [],
   "shrinker_config": [
     "-keeppackagenames java.**",
+    "-keeppackagenames j$.**",
     "-keepattributes Signature",
     "-keepattributes EnclosingMethod",
     "-keepattributes InnerClasses"