gn2bp: Generate `JniProcessor` manually

Test: update_results && m cronet_aml_components_cronet_android_cronet
Change-Id: Iefa8dd1224921cf91c075bf3347c2f5469d20eab
diff --git a/tools/gn2bp/Android.bp.swp b/tools/gn2bp/Android.bp.swp
index 35c48b5..8378cb5 100644
--- a/tools/gn2bp/Android.bp.swp
+++ b/tools/gn2bp/Android.bp.swp
@@ -9860,6 +9860,19 @@
             "base/android/java/src/",
         ],
     },
+    plugins: [
+        "cronet_aml_java_jni_annotation_preprocessor",
+    ],
+}
+
+// GN: //base/android/jni_generator:jni_processor
+java_plugin {
+    name: "cronet_aml_java_jni_annotation_preprocessor",
+    srcs: [
+        "base/android/jni_generator/java/src/org/chromium/jni_generator/JniProcessor.java",
+        "build/android/java/src/org/chromium/build/annotations/CheckDiscard.java",
+        "build/android/java/src/org/chromium/build/annotations/MainDex.java",
+    ],
 }
 
 // GN: //net/android:net_android_java_enums_srcjar