Makes the instant url managed by group policy.

chrome/browser/policy/configuration_policy_pref_store.cc

Index: chrome/browser/policy/configuration_policy_pref_store.cc
diff --git a/chrome/browser/policy/configuration_policy_pref_store.cc b/chrome/browser/policy/configuration_policy_pref_store.cc
index a942bfc2021c1ac2b2aef145404a7d6b0911af73..1bd6dc687883bab76b46288d864fcd1a8abdaa52 100644
--- a/chrome/browser/policy/configuration_policy_pref_store.cc
+++ b/chrome/browser/policy/configuration_policy_pref_store.cc
@@ -444,6 +444,7 @@ void ConfigurationPolicyPrefKeeper::FinalizeDefaultSearchPolicySettings() {
     prefs_.SetString(prefs::kDefaultSearchProviderIconURL, std::string());
     prefs_.SetString(prefs::kDefaultSearchProviderEncodings, std::string());
     prefs_.SetString(prefs::kDefaultSearchProviderKeyword, std::string());
+    prefs_.SetString(prefs::kDefaultSearchProviderInstantURL, std::string());
     return;
   }
   std::string search_url;
@@ -460,6 +461,7 @@ void ConfigurationPolicyPrefKeeper::FinalizeDefaultSearchPolicySettings() {
       EnsureStringPrefExists(prefs::kDefaultSearchProviderIconURL);
       EnsureStringPrefExists(prefs::kDefaultSearchProviderEncodings);
       EnsureStringPrefExists(prefs::kDefaultSearchProviderKeyword);
+      EnsureStringPrefExists(prefs::kDefaultSearchProviderInstantURL);
 
       // For the name, default to the host if not specified.
       std::string name;
@@ -703,6 +705,8 @@ ConfigurationPolicyPrefStore::GetChromePolicyDefinitionList() {
       key::kDefaultSearchProviderSearchURL },
     { kPolicyDefaultSearchProviderSuggestURL, Value::TYPE_STRING,
       key::kDefaultSearchProviderSuggestURL },
+    { kPolicyDefaultSearchProviderInstantURL, Value::TYPE_STRING,
+      key::kDefaultSearchProviderInstantURL },
     { kPolicyDefaultSearchProviderIconURL, Value::TYPE_STRING,
       key::kDefaultSearchProviderIconURL },
     { kPolicyDefaultSearchProviderEncodings, Value::TYPE_STRING,