Expose Physical Web metadata to native clients over JNI

chrome/browser/android/physical_web/physical_web_data_source_android.h

Index: chrome/browser/android/physical_web/physical_web_data_source_android.h
diff --git a/chrome/browser/android/physical_web/physical_web_data_source_android.h b/chrome/browser/android/physical_web/physical_web_data_source_android.h
index 8454c857cf6793ca638e0aeb1b4b01a81207e498..2a17c98ac993d88ddf306967a2a287a4225b05f7 100644
--- a/chrome/browser/android/physical_web/physical_web_data_source_android.h
+++ b/chrome/browser/android/physical_web/physical_web_data_source_android.h
@@ -34,6 +34,18 @@ class PhysicalWebDataSourceAndroid : public PhysicalWebDataSourceImpl {
   // A reference to the Java UrlManager singleton.
   base::android::ScopedJavaGlobalRef<jobject> url_manager_;
 
+  // Cached field IDs.
+  jfieldID url_infos_fid_;
+  jfieldID pws_results_fid_;
+  jfieldID url_fid_;
+  jfieldID distance_fid_;
+  jfieldID scan_timestamp_fid_;
+  jfieldID site_url_fid_;
+  jfieldID icon_url_fid_;
+  jfieldID title_fid_;
+  jfieldID description_fid_;
+  jfieldID group_id_fid_;
+
   DISALLOW_COPY_AND_ASSIGN(PhysicalWebDataSourceAndroid);
 };