Understand the support library/androidx @Keep annotations

Copied from tools/base/build-system/gradle-core/src/main/resources/com/android/build/gradle/proguard-common.txt.

Fixes: 129311848
Test: none
Change-Id: Ie8b40b416c8772a550bb4d1f7bd6e7e944cdd166

core/proguard.flags

@@ -15,4 +15,35 @@
 @**.VisibleForTesting *;
 }
 
+# Understand the @Keep support annotation.
+-keep class android.support.annotation.Keep
+-keep class androidx.annotation.Keep
+
+-keep @android.support.annotation.Keep class * {*;}
+-keep @androidx.annotation.Keep class * {*;}
+
+-keepclasseswithmembers class * {
+    @android.support.annotation.Keep <methods>;
+}
+
+-keepclasseswithmembers class * {
+    @androidx.annotation.Keep <methods>;
+}
+
+-keepclasseswithmembers class * {
+    @android.support.annotation.Keep <fields>;
+}
+
+-keepclasseswithmembers class * {
+    @androidx.annotation.Keep <fields>;
+}
+
+-keepclasseswithmembers class * {
+    @android.support.annotation.Keep <init>(...);
+}
+
+-keepclasseswithmembers class * {
+    @androidx.annotation.Keep <init>(...);
+}
+
 -include proguard_basic_keeps.flags