Don't download identical APKs on update.

chrome/browser/android/webapk/webapk_installer_unittest.cc

Index: chrome/browser/android/webapk/webapk_installer_unittest.cc
diff --git a/chrome/browser/android/webapk/webapk_installer_unittest.cc b/chrome/browser/android/webapk/webapk_installer_unittest.cc
index 84265e7d0a0d446b7e3b8837f2c185c66b221abc..62426133e4cadd6b50b1478aa61c4bd3a70d27ee 100644
--- a/chrome/browser/android/webapk/webapk_installer_unittest.cc
+++ b/chrome/browser/android/webapk/webapk_installer_unittest.cc
@@ -424,6 +424,16 @@ TEST_F(WebApkInstallerTest, UpdateSuccess) {
   EXPECT_TRUE(runner->success());
 }
 
+// Test that updates suceeded if the WebAPK server returns a HTTP response with
+// an empty download URL.

[pkotwicz, 2017/02/10 02:50:31]

Nits:
"updates" -> "an update"
"succeeded" -> "succeeds"

Can you please add:
"
The WebAPK server sends an empty download URL when:
- The server is unable to update the WebAPK in the way that the client
requested.
AND
- The most up to date version of the WebAPK on the server is identical to the
one installed on the client.
"

[Xi Han, 2017/02/10 18:21:09]

Done.

+TEST_F(WebApkInstallerTest, UpdateSuccessWithEmptyDownloadUrlInResponse) {
+  SetWebApkResponseBuilder(base::Bind(&BuildValidWebApkResponse, GURL()));
+
+  std::unique_ptr<WebApkInstallerRunner> runner = CreateWebApkInstallerRunner();
+  runner->RunUpdateWebApk();
+  EXPECT_TRUE(runner->success());
+}
+
 // Test installation succeeds using Google Play.
 TEST_F(WebApkInstallerTest, InstallFromGooglePlaySuccess) {
   std::unique_ptr<WebApkInstallerRunner> runner = CreateWebApkInstallerRunner();