[autofill] Control autofill server communciation via Finch

This CL adds a feature flag to enable/disable communication with the
autofill server. It further adds a feature parameter by which the
autofill server URL can be controlled.

This functionality is to support:

  - routing a % of users to exercise a staging server environment
    to ensure better server validation before rollout.

  - turning off or rerouting autofill server traffic from the test
    bots.

By default, autofill server communication is enabled and will send
traffic to the existing autofill server.

Bug: 874553, 866940
Change-Id: I8a425c76d483731fce9ef0ef8e10ac0cc145cb1d
Reviewed-on: https://chromium-review.googlesource.com/1176287
Commit-Queue: Roger McFarlane <rogerm@chromium.org>
Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584076}

components/autofill/core/browser/autofill_download_manager.cc

@@ -12,6 +12,7 @@
 #include "base/command_line.h"
 #include "base/location.h"
 #include "base/logging.h"
+#include "base/metrics/field_trial_params.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/numerics/safe_conversions.h"
 #include "base/rand_util.h"
@@ -75,6 +76,9 @@ const char kDefaultAutofillServerURL[] =
 
 // Returns the base URL for the autofill server.
 GURL GetAutofillServerURL() {
+  // If a valid autofill server URL is specified on the command line, then the
+  // AutofillDownlaodManager will use it, and assume that server communication
+  // is enabled.
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
   if (command_line.HasSwitch(switches::kAutofillServerURL)) {
@@ -82,13 +86,35 @@ GURL GetAutofillServerURL() {
     if (url.is_valid())
       return url;
 
-    LOG(ERROR) << "Invalid URL given for --" << switches::kAutofillServerURL
-               << ". Using default value.";
+    LOG(ERROR) << "Invalid URL value for --" << switches::kAutofillServerURL
+               << ": "
+               << command_line.GetSwitchValueASCII(
+                      switches::kAutofillServerURL);
   }
 
-  GURL default_url(kDefaultAutofillServerURL);
-  DCHECK(default_url.is_valid());
-  return default_url;
+  // If communication is disabled, leave the autofill server URL unset.
+  if (!base::FeatureList::IsEnabled(features::kAutofillServerCommunication))
+    return GURL();
+
+  // Server communication is enabled. If there's an autofill server url param
+  // use it, otherwise use the default.
+  const std::string autofill_server_url_str =
+      base::FeatureParam<std::string>(&features::kAutofillServerCommunication,
+                                      switches::kAutofillServerURL,
+                                      kDefaultAutofillServerURL)
+          .Get();
+
+  GURL autofill_server_url(autofill_server_url_str);
+
+  if (!autofill_server_url.is_valid()) {
+    LOG(ERROR) << "Invalid URL param for "
+               << features::kAutofillServerCommunication.name << "/"
+               << switches::kAutofillServerURL << ": "
+               << autofill_server_url_str;
+    return GURL();
+  }
+
+  return autofill_server_url;
 }
 
 // Helper to log the HTTP |response_code| received for |request_type| to UMA.
@@ -298,6 +324,9 @@ AutofillDownloadManager::~AutofillDownloadManager() = default;
 
 bool AutofillDownloadManager::StartQueryRequest(
     const std::vector<FormStructure*>& forms) {
+  if (!IsEnabled())
+    return false;
+
   // Do not send the request if it contains more fields than the server can
   // accept.
   if (CountActiveFieldsInForms(forms) > kMaxFieldsPerQueryRequest)
@@ -339,6 +368,9 @@ bool AutofillDownloadManager::StartUploadRequest(
     const ServerFieldTypeSet& available_field_types,
     const std::string& login_form_signature,
     bool observed_submission) {
+  if (!IsEnabled())
+    return false;
+
   AutofillUploadContents upload;
   if (!form.EncodeUploadRequest(available_field_types, form_was_autofilled,
                                 login_form_signature, observed_submission,

components/autofill/core/browser/autofill_download_manager.h

@@ -88,6 +88,9 @@ class AutofillDownloadManager {
       const std::string& login_form_signature,
       bool observed_submission);
 
+  // Returns true if the autofill server communication is enabled.
+  bool IsEnabled() const { return autofill_server_url_.is_valid(); }
+
  private:
   friend class AutofillDownloadManagerTest;
   FRIEND_TEST_ALL_PREFIXES(AutofillDownloadManagerTest, QueryAndUploadTest);
@@ -144,7 +147,7 @@ class AutofillDownloadManager {
 
   // The autofill server URL root: scheme://host[:port]/path excluding the
   // final path component for the request and the query params.
-  GURL autofill_server_url_;
+  const GURL autofill_server_url_;
 
   // Loaders used for the processing the requests. Invalidated after completion.
   std::list<std::unique_ptr<network::SimpleURLLoader>> url_loaders_;

components/autofill/core/common/autofill_features.cc

@@ -108,6 +108,15 @@ const base::Feature kAutofillSendOnlyCountryInGetUploadDetails{
     "AutofillSendOnlyCountryInGetUploadDetails",
     base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Enables or Disables (mostly for hermetic testing) autofill server
+// communication. The URL of the autofill server can further be controlled via
+// the autofill-server-url param. The given URL should specify the complete
+// autofill server API url up to the parent "directory" of the "query" and
+// "upload" resources.
+// i.e., https://other.autofill.server:port/tbproxy/af/
+const base::Feature kAutofillServerCommunication{
+    "kAutofillServerCommunication", base::FEATURE_ENABLED_BY_DEFAULT};
+
 // Controls whether we show warnings in the Dev console for misused autocomplete
 // types.
 const base::Feature kAutofillShowAutocompleteConsoleWarnings{

components/autofill/core/common/autofill_features.h

@@ -28,6 +28,7 @@ extern const base::Feature kAutofillRestrictUnownedFieldsToFormlessCheckout;
 extern const base::Feature kAutofillSaveCardSignInAfterLocalSave;
 extern const base::Feature kAutofillSendExperimentIdsInPaymentsRPCs;
 extern const base::Feature kAutofillSendOnlyCountryInGetUploadDetails;
+extern const base::Feature kAutofillServerCommunication;
 extern const base::Feature kAutofillShowAllSuggestionsOnPrefilledForms;
 extern const base::Feature kAutofillShowAutocompleteConsoleWarnings;
 extern const base::Feature kAutofillShowTypePredictions;
@@ -40,6 +41,7 @@ extern const base::Feature kAutomaticPasswordGeneration;
 extern const base::Feature kSingleClickAutofill;
 extern const base::Feature kAutofillPrefilledFields;
 extern const base::Feature kAutofillRationalizeRepeatedServerPredictions;
+
 }  // namespace features
 }  // namespace autofill