Fix dex verification error in WebLayer.java

The attribution methods are only available in R, so add a ApiHelperForR
class to access them.

Bug: 1085041
Change-Id: Ief6957ad59cd499111c96a7a171eb2dca8e3d609
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2570034Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Clark DuVall <cduvall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833335}

weblayer/public/java/BUILD.gn

@@ -99,6 +99,7 @@ android_library("java") {
     "org/chromium/weblayer/UrlBarOptions.java",
     "org/chromium/weblayer/UserIdentityCallback.java",
     "org/chromium/weblayer/VerifiesOnO.java",
+    "org/chromium/weblayer/VerifiesOnR.java",
     "org/chromium/weblayer/WebLayer.java",
     "org/chromium/weblayer/WebLayerFileProvider.java",
     "org/chromium/weblayer/WebMessage.java",

weblayer/public/java/org/chromium/weblayer/VerifiesOnR.java

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package org.chromium.weblayer;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * The annotated method or class verifies on R, but not below.
+ *
+ * The annotated method (or methods on the annotated class) are guaranteed to not be inlined by R8
+ * on builds targeted below R. This prevents class verification errors (which results in a very slow
+ * retry-verification-at-runtime) from spreading into other classes on these lower versions.
+ *
+ * Note: this is the WebLayer client library version of the annotation from
+ * org.chromium.base.annotations.
+ */
+@Target({ElementType.CONSTRUCTOR, ElementType.METHOD, ElementType.TYPE})
+@Retention(RetentionPolicy.CLASS)
+/* package */ @interface VerifiesOnR {}

weblayer/public/java/org/chromium/weblayer/WebLayer.java

@@ -273,11 +273,12 @@ public class WebLayer {
             // Use the application context as the supplied context may have a shorter lifetime.
             mContext = context.getApplicationContext();
             if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R
-                    && context.getAttributionTag() != null) {
+                    && ApiHelperForR.getAttributionTag(context) != null) {
                 // Getting the application context means we lose any attribution. Use the
                 // attribution tag from the supplied context so that embedders have a way to set an
                 // attribution tag.
-                mContext = mContext.createAttributionContext(context.getAttributionTag());
+                mContext = ApiHelperForR.createAttributionContext(
+                        mContext, ApiHelperForR.getAttributionTag(context));
             }
             try {
                 ClassLoader classLoader = getOrCreateRemoteClassLoader(mContext);
@@ -835,4 +836,18 @@ public class WebLayer {
             }
         }
     }
+
+    @VerifiesOnR
+    @TargetApi(Build.VERSION_CODES.R)
+    private static final class ApiHelperForR {
+        /** See {@link Context.getAttributionTag() }. */
+        public static String getAttributionTag(Context context) {
+            return context.getAttributionTag();
+        }
+
+        /** See {@link Context.createAttributionContext(String) }. */
+        public static Context createAttributionContext(Context context, String tag) {
+            return context.createAttributionContext(tag);
+        }
+    }
 }

weblayer/public/java/proguard.flags

@@ -12,3 +12,14 @@
 -keepclassmembers,allowobfuscation class ** {
   @org.chromium.weblayer.VerifiesOnO <methods>;
 }
+
+-keep @interface org.chromium.weblayer.VerifiesOnR
+-if @org.chromium.weblayer.VerifiesOnR class * {
+    *** *(...);
+}
+-keep,allowobfuscation class <1> {
+    *** <2>(...);
+}
+-keepclassmembers,allowobfuscation class ** {
+  @org.chromium.weblayer.VerifiesOnR <methods>;
+}