Create a Finch experiment to turn on JSON in the update client.

Bug: 881076
Change-Id: I9f9739197c903cce7b0814b54df4314d2917b6eb
Reviewed-on: https://chromium-review.googlesource.com/c/1334969Reviewed-by: Joshua Pawlicki <waffles@chromium.org>
Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
Commit-Queue: Sorin Jianu <sorin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608432}

components/component_updater/component_updater_url_constants.cc

@@ -20,4 +20,10 @@ const char kUpdaterDefaultUrl[] =
 const char kUpdaterFallbackUrl[] =
     "http://update.googleapis.com/service/update2";
 
+extern const char kUpdaterJSONDefaultUrl[] =
+    "https://update.googleapis.com/service/update2/json";
+
+extern const char kUpdaterJSONFallbackUrl[] =
+    "http://update.googleapis.com/service/update2/json";
+
 }  // namespace component_updater

components/component_updater/component_updater_url_constants.h

@@ -7,9 +7,14 @@
 
 namespace component_updater {
 
+// Xml endpoints.
 extern const char kUpdaterDefaultUrl[];
 extern const char kUpdaterFallbackUrl[];
 
+// JSON endpoints.
+extern const char kUpdaterJSONDefaultUrl[];
+extern const char kUpdaterJSONFallbackUrl[];
+
 }  // namespace component_updater
 
 #endif  // COMPONENTS_COMPONENT_UPDATER_COMPONENT_UPDATER_URL_CONSTANTS_H_

components/component_updater/configurator_impl.cc

@@ -8,6 +8,7 @@
 
 #include <algorithm>
 
+#include "base/feature_list.h"
 #include "base/stl_util.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
@@ -32,6 +33,13 @@ namespace {
 const int kDelayOneMinute = 60;
 const int kDelayOneHour = kDelayOneMinute * 60;
 
+// Enables using JSON as an update client protocol encoding instead of XML.
+//
+// The JSON implementation is available behind a flag:
+// --enable-features=UpdateClientUseJSON
+const base::Feature kFeatureUpdateClientUseJSON{
+    "UpdateClientUseJSON", base::FEATURE_DISABLED_BY_DEFAULT};
+
 }  // namespace
 
 ConfiguratorImpl::ConfiguratorImpl(
@@ -69,11 +77,15 @@ int ConfiguratorImpl::UpdateDelay() const {
 }
 
 std::vector<GURL> ConfiguratorImpl::UpdateUrl() const {
-  if (url_source_override_.is_valid()) {
+  if (url_source_override_.is_valid())
     return {GURL(url_source_override_)};
-  }
 
-  std::vector<GURL> urls{GURL(kUpdaterDefaultUrl), GURL(kUpdaterFallbackUrl)};
+  std::vector<GURL> urls =
+      base::FeatureList::IsEnabled(kFeatureUpdateClientUseJSON)
+          ? std::vector<GURL>{GURL(kUpdaterJSONDefaultUrl),
+                              GURL(kUpdaterJSONFallbackUrl)}
+          : std::vector<GURL>{GURL(kUpdaterDefaultUrl),
+                              GURL(kUpdaterFallbackUrl)};
   if (require_encryption_)
     update_client::RemoveUnsecureUrls(&urls);
 
@@ -133,6 +145,8 @@ std::string ConfiguratorImpl::GetAppGuid() const {
 
 std::unique_ptr<update_client::ProtocolHandlerFactory>
 ConfiguratorImpl::GetProtocolHandlerFactory() const {
+  if (base::FeatureList::IsEnabled(kFeatureUpdateClientUseJSON))
+    return std::make_unique<update_client::ProtocolHandlerFactoryJSON>();
   return std::make_unique<update_client::ProtocolHandlerFactoryXml>();
 }
 

testing/variations/fieldtrial_testing_config.json

@@ -4981,6 +4981,26 @@
             ]
         }
     ],
+    "UpdateClientUseJSON": [
+        {
+            "platforms": [
+                "android",
+                "chromeos",
+                "linux",
+                "mac",
+                "windows",
+                "ios"
+            ],
+            "experiments": [
+                {
+                    "name": "UpdateClientUseJSON",
+                    "enable_features": [
+                        "UpdateClientUseJSON"
+                    ]
+                }
+            ]
+        }
+    ],
     "UpdateMenuItem": [
         {
             "platforms": [