[Cronet] add base proguard flags

components/cronet/android/proguard.cfg

Index: components/cronet/android/proguard.cfg
diff --git a/components/cronet/android/proguard.cfg b/components/cronet/android/proguard.cfg
index 853747da727ba837b7ba46d15954389f0584a4a1..4ca24c078c6a2bfa0b693e96c958836c845a2750 100644
--- a/components/cronet/android/proguard.cfg
+++ b/components/cronet/android/proguard.cfg
@@ -1,35 +1,6 @@
-# Keep annotations used by chromium to keep members referenced by native code
--keep class org.chromium.base.annotations.*Native*
--keep class org.chromium.base.annotations.JNINamespace
--keepclasseswithmembers class org.chromium.** {
-    @org.chromium.base.annotations.AccessedByNative <fields>;
-}
--keepclasseswithmembers class org.chromium.** {
-    @org.chromium.base.annotations.*Native* <methods>;
-}
-
-# TODO(mef) remove unnecessary classes from base, so we don't have to preserve
-# their methods
--keepclasseswithmembers class org.chromium.** {
-    native <methods>;
-}
-
-# TODO(xunjieli): Find an alternative to explictly preserving public classes.
--keep public class org.chromium.net.*
-
 -keep class org.chromium.net.impl.CronetUrlRequest$HeadersList
 -keep class org.chromium.net.impl.ChromiumUrlRequest$ResponseHeadersMap
 
-# Needed so that multiple optimization passes will detect annotations
--keepattributes *Annotation*
-
-# Keep methods used by reflection
--keep class org.chromium.base.annotations.UsedByReflection
--keep @org.chromium.base.annotations.UsedByReflection class *
--keepclassmembers class * {
-    @org.chromium.base.annotations.UsedByReflection *;
-}
-
 # Suppress unnecessary warnings.
 -dontnote org.chromium.net.ProxyChangeListener$ProxyReceiver
 -dontnote org.chromium.net.AndroidKeyStore