Experimental Contextual ZS suggestions - add new field trial param.

This CL adds a new field trial param that allows to use a separate
server for requests coming from Dev/Canary and Stable users.

Bug: 692471
Change-Id: I9774ef54f3f4d1778492b84840e24804cb08705f
Reviewed-on: https://chromium-review.googlesource.com/728405
Commit-Queue: Gheorghe Comanici <gcomanici@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510263}

components/omnibox/browser/contextual_suggestions_service.cc

@@ -24,7 +24,7 @@
 namespace {
 
 // Server address for the experimental suggestions service.
-const char kExperimentalServerAddress[] =
+const char kDefaultExperimentalServerAddress[] =
     "https://cuscochromeextension-pa.googleapis.com/v1/omniboxsuggestions";
 
 void AddVariationHeaders(std::unique_ptr<net::URLFetcher>& fetcher) {
@@ -161,7 +161,11 @@ GURL ContextualSuggestionsService::ExperimentalContextualSuggestionsUrl(
     return GURL();
   }
 
-  GURL suggest_url(kExperimentalServerAddress);
+  const std::string server_address_param =
+      OmniboxFieldTrial::GetZeroSuggestRedirectToChromeServerAddress();
+  GURL suggest_url(server_address_param.empty()
+                       ? kDefaultExperimentalServerAddress
+                       : server_address_param);
   // Check that the suggest URL for redirect to chrome field trial is valid.
   if (!suggest_url.is_valid()) {
     return GURL();

components/omnibox/browser/omnibox_field_trial.cc

@@ -352,10 +352,17 @@ bool OmniboxFieldTrial::InZeroSuggestPersonalizedFieldTrial(
 int OmniboxFieldTrial::GetZeroSuggestRedirectToChromeExperimentId() {
   return base::GetFieldTrialParamByFeatureAsInt(
       omnibox::kZeroSuggestRedirectToChrome,
-      OmniboxFieldTrial::kZeroSuggestRedirectToChromeExperimentIdParam,
+      kZeroSuggestRedirectToChromeExperimentIdParam,
       /*default_value=*/-1);
 }
 
+// static
+std::string OmniboxFieldTrial::GetZeroSuggestRedirectToChromeServerAddress() {
+  return base::GetFieldTrialParamValueByFeature(
+      omnibox::kZeroSuggestRedirectToChrome,
+      kZeroSuggestRedirectToChromeServerAddressParam);
+}
+
 bool OmniboxFieldTrial::ShortcutsScoringMaxRelevance(
     OmniboxEventProto::PageClassification current_page_classification,
     int* max_relevance) {
@@ -825,6 +832,8 @@ const char OmniboxFieldTrial::kUIVerticalMarginParam[] = "UIVerticalMargin";
 
 const char OmniboxFieldTrial::kZeroSuggestRedirectToChromeExperimentIdParam[] =
     "ZeroSuggestRedirectToChromeExperimentID";
+const char OmniboxFieldTrial::kZeroSuggestRedirectToChromeServerAddressParam[] =
+    "ZeroSuggestRedirectToChromeServerAddress";
 
 // static
 int OmniboxFieldTrial::kDefaultMinimumTimeBetweenSuggestQueriesMs = 100;

components/omnibox/browser/omnibox_field_trial.h

@@ -216,6 +216,9 @@ class OmniboxFieldTrial {
   // Returns -1 if there is no associated experiment ID.
   static int GetZeroSuggestRedirectToChromeExperimentId();
 
+  // Returns the server address associated with the current field trial.
+  static std::string GetZeroSuggestRedirectToChromeServerAddress();
+
   // ---------------------------------------------------------
   // For the ShortcutsScoringMaxRelevance experiment that's part of the
   // bundled omnibox field trial.
@@ -505,6 +508,7 @@ class OmniboxFieldTrial {
 
   // Parameter names used by Zero Suggest Redirect to Chrome.
   static const char kZeroSuggestRedirectToChromeExperimentIdParam[];
+  static const char kZeroSuggestRedirectToChromeServerAddressParam[];
 
   // The amount of time to wait before sending a new suggest request after the
   // previous one unless overridden by a field trial parameter.