Refactor base's proguard flags to be more usable by cronet

base/android/base_proguard_config.flags

-# Keep line number information, useful for stack traces.
--keepattributes SourceFile,LineNumberTable
-
-# Keep all annotation related attributes that can affect runtime
--keepattributes RuntimeVisible*Annotations
--keepattributes AnnotationDefault
-
-# Keep the annotations, because if we don't, the ProGuard rules that use them
-# will not be respected. These classes then show up in our final dex, which we
-# do not want - see crbug.com/628226.
--keep @interface org.chromium.base.annotations.AccessedByNative
--keep @interface org.chromium.base.annotations.CalledByNative
--keep @interface org.chromium.base.annotations.CalledByNativeUnchecked
--keep @interface org.chromium.base.annotations.RemovableInRelease
--keep @interface org.chromium.base.annotations.UsedByReflection
-
-# Keeps for class level annotations.
--keep @org.chromium.base.annotations.UsedByReflection class *
-
-# Keeps for method level annotations.
--keepclasseswithmembers class * {
-  @org.chromium.base.annotations.AccessedByNative <fields>;
-}
--keepclasseswithmembers,includedescriptorclasses class * {
-  @org.chromium.base.annotations.CalledByNative <methods>;
-}
--keepclasseswithmembers,includedescriptorclasses class * {
-  @org.chromium.base.annotations.CalledByNativeUnchecked <methods>;
-}
--keepclasseswithmembers class * {
-  @org.chromium.base.annotations.UsedByReflection <methods>;
-}
--keepclasseswithmembers,includedescriptorclasses class * {
-  native <methods>;
-}
-
-# Keep all CREATOR fields within Parcelable that are kept.
--keepclassmembers class * implements android.os.Parcelable {
-  public static *** CREATOR;
-}
-
-# Don't obfuscate Parcelables as they might be marshalled outside Chrome.
-# If we annotated all Parcelables that get put into Bundles other than
-# for saveInstanceState (e.g. PendingIntents), then we could actually keep the
-# names of just those ones. For now, we'll just keep them all.
--keepnames class * implements android.os.Parcelable
-
-# Remove methods annotated with this if their return value is unused
--assumenosideeffects class ** {
-  @org.chromium.base.annotations.RemovableInRelease <methods>;
-}
-
-# Keep all enum values and valueOf methods. See
-# http://proguard.sourceforge.net/index.html#manual/examples.html
-# for the reason for this. Also, see http://crbug.com/248037.
--keepclassmembers enum * {
-    public static **[] values();
-}
-