Pass Physical Web metadata through a struct

ios/chrome/browser/physical_web/ios_chrome_physical_web_data_source.mm

Index: ios/chrome/browser/physical_web/ios_chrome_physical_web_data_source.mm
diff --git a/ios/chrome/browser/physical_web/ios_chrome_physical_web_data_source.mm b/ios/chrome/browser/physical_web/ios_chrome_physical_web_data_source.mm
index f2dcdeea51e9cca922f4e3948db359491f40c947..250640d4df577bf53b2ca8936540d36e1290a6ba 100644
--- a/ios/chrome/browser/physical_web/ios_chrome_physical_web_data_source.mm
+++ b/ios/chrome/browser/physical_web/ios_chrome_physical_web_data_source.mm
@@ -52,6 +52,14 @@ std::unique_ptr<base::ListValue> IOSChromePhysicalWebDataSource::GetMetadata() {
   return [scanner_ metadata];
 }
 
+std::unique_ptr<MetadataList>

[mattreynolds, 2017/01/11 20:54:50]

physical_web:: (here and in the MakeUnique call below)

[cco3, 2017/01/11 22:51:02]

Done.

+IOSChromePhysicalWebDataSource::GetMetadataList() {
+  if (!scanner_) {
+    return base::MakeUnique<MetadataList>();
+  }
+  return [scanner_ metadataList];
+}
+
 bool IOSChromePhysicalWebDataSource::HasUnresolvedDiscoveries() {
   return [scanner_ unresolvedBeaconsCount] > 0;
 }