Fixing WebView ProGuard config for annotations

android_webview/apk/java/proguard.flags

 # Don't rename anything, it makes stack traces unintelligible. We only allow the
 # obfuscation pass to run so that we can discard attributes like local variable
 # tables.
 -keepnames class *** { *; }
 
 # Keep source file and line number information for stack traces.
 -keepattributes SourceFile,LineNumberTable
 
 # Keep all runtime visible annotations.
 -keepattributes RuntimeVisibleAnnotations
-
-# Disable optimization as this causes proguard to remove seemingly random stuff,
-# including things explicitly kept in this configuration.
--dontoptimize
+# Keeping annotations - if we remove these keeps, ProGuard will eliminate the
+# annotations themselves, which will prevent them from affecting ProGuard's
+# optimization run.
+-keep @interface **.AccessedByNative
+-keep @interface **.CalledByNative
+-keep @interface **.CalledByNativeUnchecked
+-keep @interface **.RemovableInRelease
+-keep @interface **.UsedByReflection
 
 # Keep the factory and its public members; it's the main entry point used by the
 # framework.
 -keep class com.android.webview.chromium.WebViewChromiumFactoryProvider {
     public *;
 }
 
 # This is the main entry point for APIs. It is kept to make developing with
 # unreleased Android easier.
 -keep class com.android.webview.chromium.WebViewChromium {
   public *;
 }
 
 # Keep JNI interfaces.
 -keepclasseswithmembers class com.android.webview.chromium.**,org.chromium.** {
   @**.AccessedByNative <fields>;
 }
 -keepclasseswithmembers class com.android.webview.chromium.**,org.chromium.** {
   @**.CalledByNative <methods>;
 }
 -keepclasseswithmembers class com.android.webview.chromium.**,org.chromium.** {
   @**.CalledByNativeUnchecked <methods>;
 }
 -keepclasseswithmembers class com.android.webview.chromium.**,org.chromium.** {
   native <methods>;
 }
 
-# Keep things explicitly marked as used by reflection
+# Keep classes marked as used by reflection
+-keep @**.UsedByReflection class com.android.webview.chromium.**,org.chromium.**
+
+# Keep members explicitly marked as used by reflection
 -keepclasseswithmembers class com.android.webview.chromium.**,org.chromium.** {
   @**.UsedByReflection *;
 }
 
+# Remove methods annotated with this if their return value is unused
+-assumenosideeffects class ** {
+  @org.chromium.base.annotations.RemovableInRelease <methods>;
+}
+
 # Linker dynamically casts to $TestRunner when running tests. We don't run these
 # tests in WebView.
 -dontnote org.chromium.base.library_loader.Linker$TestRunner
 
 # Don't note about the API 21 compatibility code which references various
 # hidden APIs via reflection.
 -dontnote com.android.webview.chromium.WebViewDelegateFactory$Api21CompatibilityDelegate
 
 # DefaultAndroidKeyStore uses reflection to access internal OpenSSL state.
 -dontnote org.chromium.net.DefaultAndroidKeyStore
@@ skipping 35 matching lines @@
 -dontnote android.support.**
 -dontwarn android.support.**
 
 # 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();
     public static ** valueOf(java.lang.String);
 }