[android] Proguard out most of guava

third_party/guava/proguard.flags

Index: third_party/guava/proguard.flags
diff --git a/third_party/guava/proguard.flags b/third_party/guava/proguard.flags
index e97f99db26bba5788d5d6efa96e993937a17887f..5bcdb20492ee7ef048b820a0a866688b5691cd31 100644
--- a/third_party/guava/proguard.flags
+++ b/third_party/guava/proguard.flags
@@ -2,12 +2,12 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
--keep class com.google.common.base.** {
-  *;
-}
-
--keep class com.google.common.annotations.** {
-  *;
+-keep class com.google.common.annotations.VisibleForTesting,
+            com.google.common.base.Preconditions,
+            com.google.common.base.Objects,
+            com.google.common.base.Strings,
+            com.google.common.base.Supplier {
+    *;
 }
 
 -keepattributes Signature