Implement chrome.systemPrivate.getIncognitoModeAvailability extension API function

chrome/browser/extensions/extension_preference_api.cc

Index: chrome/browser/extensions/extension_preference_api.cc
diff --git a/chrome/browser/extensions/extension_preference_api.cc b/chrome/browser/extensions/extension_preference_api.cc
index 871d99bcac5fca3cc678cfa9226c7510fe0f745a..b6421c804fd8a0f0e4565690f18fdcc5ab593e22 100644
--- a/chrome/browser/extensions/extension_preference_api.cc
+++ b/chrome/browser/extensions/extension_preference_api.cc
@@ -29,8 +29,15 @@
 namespace {
 
 struct PrefMappingEntry {
+  // Name of the preference referenced by extension_api.json.
   const char* extension_pref;
+
+  // Name of the preference in the PrefStores.
   const char* browser_pref;
+
+  // Permission required to access this preference.
+  // Use ExtensionAPIPermission::kInvalid for |permission| to express that no
+  // permission is necessary.
   ExtensionAPIPermission::ID permission;
 };
 
@@ -45,6 +52,10 @@ const char kValue[] = "value";
 
 const char kOnPrefChangeFormat[] = "types.ChromeSetting.%s.onChange";
 
+const char* kReadOnlyPrefs[] = {
+    prefs::kIncognitoModeAvailability
+};
+
 PrefMappingEntry kPrefMapping[] = {
   { "alternateErrorPagesEnabled",
     prefs::kAlternateErrorPagesEnabled,
@@ -94,9 +105,21 @@ PrefMappingEntry kPrefMapping[] = {
   { "translationServiceEnabled",
     prefs::kEnableTranslate,
     ExtensionAPIPermission::kExperimental
+  },
+  { "incognitoModeAvailability",
+    prefs::kIncognitoModeAvailability,
+    ExtensionAPIPermission::kInvalid  // kInvalid = none required.
   }
 };
 
+// Maps prefs::kIncognitoModeAvailability values (0 = enabled, ...)
+// to strings exposed to extensions.
+const char* kIncognitoModeAvailabilityStrings[] = {
+  "enabled",
+  "disabled",
+  "forced"
+};
+
 class IdentityPrefTransformer : public PrefTransformerInterface {
  public:
   virtual Value* ExtensionToBrowserPref(const Value* extension_pref,
@@ -131,6 +154,47 @@ class InvertBooleanTransformer : public PrefTransformerInterface {
   }
 };
 
+class IncognitoModeAvailabilityTransformer : public PrefTransformerInterface {
+ public:
+  virtual Value* ExtensionToBrowserPref(const Value* extension_pref,
+                                        std::string* error,
+                                        bool* bad_message) {
+    // We do not allow extensions to modify the IncognitoModeAvailability
+    // preference. Therefore, this function is never called.
+    NOTREACHED();
+    return NULL;
+  }
+
+  virtual Value* BrowserToExtensionPref(const Value* browser_pref) {
+    int browser_pref_value;
+    if (!browser_pref->GetAsInteger(&browser_pref_value) ||
+        browser_pref_value < 0 ||
+        browser_pref_value >=
+            static_cast<int>(arraysize(kIncognitoModeAvailabilityStrings))) {
+      return NULL;
+    }
+    return Value::CreateStringValue(
+        kIncognitoModeAvailabilityStrings[browser_pref_value]);
+  }
+};
+
+// Checks whether an extension has a specific permission but considers
+// ExtensionAPIPermission::kInvalid a wildcard that is possessed by every
+// extension.
+bool HasAPIPermission(const Extension* extension,
+                      ExtensionAPIPermission::ID permission) {
+  return permission == ExtensionAPIPermission::kInvalid ||
+         extension->HasAPIPermission(permission);
+}
+
+bool IsReadOnlyPreference(const std::string& browser_pref) {
+    for (size_t i = 0; i < arraysize(kReadOnlyPrefs); ++i) {

[Bernhard Bauer, 2011/11/23 15:53:57]

Nit: Indent only two spaces.

[battre, 2011/11/23 15:56:05]

Done.

+      if (kReadOnlyPrefs[i] == browser_pref)
+        return true;
+    }
+    return false;
+}
+
 // Returns a string constant (defined in the API) indicating the level of
 // control this extension has over the specified preference.
 const char* GetLevelOfControl(
@@ -145,6 +209,9 @@ const char* GetLevelOfControl(
   CHECK(pref);
   ExtensionPrefs* ep = profile->GetExtensionService()->extension_prefs();
 
+  if (IsReadOnlyPreference(browser_pref))
+    return kNotControllable;
+
   if (!pref->IsExtensionModifiable())
     return kNotControllable;
 
@@ -216,7 +283,9 @@ class PrefMapping {
     DCHECK_EQ(arraysize(kPrefMapping), event_mapping_.size());
     RegisterPrefTransformer(prefs::kProxy, new ProxyPrefTransformer());
     RegisterPrefTransformer(prefs::kBlockThirdPartyCookies,
-                            new InvertBooleanTransformer());
+        new InvertBooleanTransformer());
+    RegisterPrefTransformer(prefs::kIncognitoModeAvailability,
+        new IncognitoModeAvailabilityTransformer());
   }
 
   ~PrefMapping() {
@@ -315,7 +384,7 @@ void ExtensionPreferenceEventRouter::OnPrefChanged(
     std::string extension_id = (*it)->id();
     // TODO(bauerb): Only iterate over registered event listeners.
     if (router->ExtensionHasEventListener(extension_id, event_name) &&
-        (*it)->HasAPIPermission(permission) &&
+        HasAPIPermission(it->get(), permission) &&
         (!incognito || extension_service->CanCrossIncognito(*it))) {
       std::string level_of_control =
           GetLevelOfControl(profile_, extension_id, browser_pref, incognito);
@@ -364,7 +433,7 @@ bool GetPreferenceFunction::RunImpl() {
   EXTENSION_FUNCTION_VALIDATE(
       PrefMapping::GetInstance()->FindBrowserPrefForExtensionPref(
           pref_key, &browser_pref, &permission));
-  if (!GetExtension()->HasAPIPermission(permission)) {
+  if (!HasAPIPermission(GetExtension(), permission)) {
     error_ = ExtensionErrorUtils::FormatErrorMessage(
         keys::kPermissionErrorMessage, pref_key);
     return false;
@@ -438,11 +507,18 @@ bool SetPreferenceFunction::RunImpl() {
   EXTENSION_FUNCTION_VALIDATE(
       PrefMapping::GetInstance()->FindBrowserPrefForExtensionPref(
           pref_key, &browser_pref, &permission));
-  if (!GetExtension()->HasAPIPermission(permission)) {
+  if (!HasAPIPermission(GetExtension(), permission)) {
     error_ = ExtensionErrorUtils::FormatErrorMessage(
         keys::kPermissionErrorMessage, pref_key);
     return false;
   }
+
+  if (IsReadOnlyPreference(browser_pref)) {
+    error_ = ExtensionErrorUtils::FormatErrorMessage(
+        keys::kCannotModifyReadOnlyMessage, pref_key);
+    return false;
+  }
+
   ExtensionPrefs* prefs = profile_->GetExtensionService()->extension_prefs();
   const PrefService::Preference* pref =
       prefs->pref_service()->FindPreference(browser_pref.c_str());
@@ -502,11 +578,18 @@ bool ClearPreferenceFunction::RunImpl() {
   EXTENSION_FUNCTION_VALIDATE(
       PrefMapping::GetInstance()->FindBrowserPrefForExtensionPref(
           pref_key, &browser_pref, &permission));
-  if (!GetExtension()->HasAPIPermission(permission)) {
+  if (!HasAPIPermission(GetExtension(), permission)) {
     error_ = ExtensionErrorUtils::FormatErrorMessage(
         keys::kPermissionErrorMessage, pref_key);
     return false;
   }
+
+  if (IsReadOnlyPreference(browser_pref)) {
+    error_ = ExtensionErrorUtils::FormatErrorMessage(
+        keys::kCannotModifyReadOnlyMessage, pref_key);
+    return false;
+  }
+
   ExtensionPrefs* prefs = profile_->GetExtensionService()->extension_prefs();
   prefs->RemoveExtensionControlledPref(extension_id(), browser_pref, scope);
   return true;