Keep classes/fields only used via reflection

Bug: 30355720
Change-Id: I9c8325a0b42cda5beeb8dfe76bde46afd2bec727

proguard.flags

@@ -27,3 +27,15 @@
 -keepclasseswithmembers class * {
     public <init>(android.content.Context, android.util.AttributeSet, int);
 }
+
+# Keep annotated classes or class members.
+-keep @android.support.annotation.Keep class *
+-keepclassmembers class * {
+    @android.support.annotation.Keep *;
+}
+
+# Keep specific fields used via reflection.
+-keepclassmembers class * {
+    public static ** SEARCH_INDEX_DATA_PROVIDER;
+    public static ** SUMMARY_PROVIDER_FACTORY;
+}

src/com/android/settings/overlay/FeatureFactoryImpl.java

@@ -17,10 +17,12 @@
 package com.android.settings.overlay;
 
 import android.content.Context;
+import android.support.annotation.Keep;
 
 /**
  * {@link FeatureFactory} implementation for AOSP Settings.
  */
+@Keep
 public final class FeatureFactoryImpl extends FeatureFactory {
 
     @Override