Don't retry an empty proxy config

This allows the config server to send an empty config in order to
effectivly turn off DataSaver if needed.

Bug: 840978
Change-Id: I7b5e57728737401c286da29ccbd7cc4564c73732
Reviewed-on: https://chromium-review.googlesource.com/1050805
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557221}

components/data_reduction_proxy/core/browser/data_reduction_proxy_config_service_client.cc

@@ -555,12 +555,11 @@ bool DataReductionProxyConfigServiceClient::ParseAndApplyProxyConfig(
   if (!config.has_proxy_config())
     return false;
 
+  // An empty proxy config is OK, and allows the server to effectively turn off
+  // DataSaver if needed. See http://crbug.com/840978.
   std::vector<DataReductionProxyServer> proxies =
       GetProxiesForHTTP(config.proxy_config());
 
-  if (proxies.empty())
-    return false;
-
   request_options_->SetSecureSession(config.session_key());
   config_values_->UpdateValues(proxies);
   config_->OnNewClientConfigFetched();

components/data_reduction_proxy/core/browser/data_reduction_proxy_config_service_client_unittest.cc

@@ -229,6 +229,13 @@ class DataReductionProxyConfigServiceClientTest : public testing::Test {
     half_reporting_fraction_encoded_config_ =
         EncodeConfig(half_reporting_fraction_config);
 
+    ClientConfig no_proxies_config;
+    no_proxies_config.set_session_key(kSuccessSessionKey);
+    no_proxies_config.mutable_refresh_duration()->set_seconds(
+        kConfigRefreshDurationSeconds);
+    no_proxies_config.mutable_refresh_duration()->set_nanos(0);
+    no_proxies_config_ = EncodeConfig(no_proxies_config);
+
     success_reads_[0] = net::MockRead("HTTP/1.1 200 OK\r\n\r\n");
     success_reads_[1] =
         net::MockRead(net::ASYNC, config_.c_str(), config_.length());
@@ -447,6 +454,7 @@ class DataReductionProxyConfigServiceClientTest : public testing::Test {
   const std::string& half_reporting_fraction_encoded_config() const {
     return half_reporting_fraction_encoded_config_;
   }
+  const std::string& no_proxies_config() const { return no_proxies_config_; }
 
   const std::string& loaded_config() const { return loaded_config_; }
 
@@ -490,6 +498,9 @@ class DataReductionProxyConfigServiceClientTest : public testing::Test {
   // A configuration where the pingback reporting fraction is set to 0.5f.
   std::string half_reporting_fraction_encoded_config_;
 
+  // A configuration where no proxies are configured.
+  std::string no_proxies_config_;
+
   // Mock socket data.
   std::vector<std::unique_ptr<net::SocketDataProvider>> socket_data_providers_;
 
@@ -1359,6 +1370,16 @@ TEST_F(DataReductionProxyConfigServiceClientTest,
   EXPECT_EQ(0.5f, pingback_reporting_fraction());
 }
 
+TEST_F(DataReductionProxyConfigServiceClientTest, EmptyConfigDisablesDRP) {
+  Init(true);
+  SetDataReductionProxyEnabled(true, true);
+  EXPECT_EQ(std::vector<net::ProxyServer>(), GetConfiguredProxiesForHttp());
+
+  config_client()->ApplySerializedConfig(no_proxies_config());
+  EXPECT_EQ(std::vector<net::ProxyServer>(), GetConfiguredProxiesForHttp());
+  EXPECT_TRUE(configurator()->GetProxyConfig().proxy_rules().empty());
+}
+
 #if defined(OS_ANDROID)
 // Verifies the correctness of fetching config when Chromium is in background
 // and foreground.