Add search_terms_replacement_key field to TemplateURL.

chrome/test/data/policy/policy_test_cases.json

 {
   "-- Template --": {
     "intro": "Top-level entries map a policy name to its test parameters, described below.",
 
     "os": ["List of operating systems that support this policy. Valid values:", "win", "linux", "mac", "chromeos", "Defaults to empty if not specified."],
     "official_only": "Whether this policy exists in official builds only. Defaults to |false| if not specified.",
     "can_be_recommended": "Whether a recommended value may be set for the policy. Defaults to |false| if not specified.",
     "test_policy": "A policy dictionary that should make the preferences affected by this policy become policy-controlled. Usually just sets the current policy. Defaults to an empty dictionary if not specified.",
     "note": "If the policy affects any preferences, the following array should be specified with one entry per such preference.",
     "pref_mappings": [
@@ skipping 759 matching lines @@
   },
 
   "DefaultSearchProviderAlternateURLs": {
     "os": ["win", "linux", "mac", "chromeos"],
     "test_policy": { "DefaultSearchProviderSearchURL": "http://www.google.com/?q={searchTerms}", "DefaultSearchProviderAlternateURLs": ["http://www.google.com/#q={searchTerms}", "http://www.google.com/search#q={searchTerms}"] },
     "pref_mappings": [
       { "pref": "default_search_provider.alternate_urls" }
     ]
   },
 
+  "DefaultSearchProviderSearchTermsReplacementKey": {
+    "os": ["win", "linux", "mac", "chromeos"],
+    "test_policy": { "DefaultSearchProviderSearchURL": "http://www.google.com/?q={searchTerms}", "DefaultSearchProviderSearchTermsReplacementKey": "espv" },
+    "pref_mappings": [
+      { "pref": "default_search_provider.search_terms_replacement_key" }
+    ]
+  },
+
   "DefaultCookiesSetting": {
     "os": ["win", "linux", "mac", "chromeos"],
     "test_policy": { "DefaultCookiesSetting": 2 },
     "pref_mappings": [
       { "pref": "profile.managed_default_content_settings.cookies",
         "indicator_selector": "[content-setting=cookies]",
         "indicator_tests": [
           { "policy": { "DefaultCookiesSetting": 1 },
             "value": "allow"},
           { "policy": { "DefaultCookiesSetting": 2 },
@@ skipping 866 matching lines @@
 
   "ChromeFrameContentTypes": {
   },
 
   "GCFUserDataDir": {
   },
 
   "AdditionalLaunchParameters": {
   }
 }