Don't download identical APKs on update.

chrome/browser/android/webapk/webapk_installer.cc

Index: chrome/browser/android/webapk/webapk_installer.cc
diff --git a/chrome/browser/android/webapk/webapk_installer.cc b/chrome/browser/android/webapk/webapk_installer.cc
index 1384c5997f700cfa52b0ab58ec16c26684fcbb19..575f02e98f0588bfdb6e2dc91675b6fa7f30187a 100644
--- a/chrome/browser/android/webapk/webapk_installer.cc
+++ b/chrome/browser/android/webapk/webapk_installer.cc
@@ -418,6 +418,13 @@ void WebApkInstaller::OnURLFetchComplete(const net::URLFetcher* source) {
   }
 
   GURL signed_download_url(response->signed_download_url());
+  // https://crbug.com/680131. The server sends an empty URL if the server does
+  // not have a newer WebAPK to update to.
+  if (task_type_ == UPDATE && signed_download_url.is_empty()) {
+    OnSuccess();
+    return;
+  }
+
   if (!signed_download_url.is_valid() || response->package_name().empty()) {
     OnFailure();
     return;