Extension Storage API: expose storage quota information to extensions, via:

chrome/browser/extensions/settings/settings_frontend.cc

Index: chrome/browser/extensions/settings/settings_frontend.cc
diff --git a/chrome/browser/extensions/settings/settings_frontend.cc b/chrome/browser/extensions/settings/settings_frontend.cc
index 8d7d914cff0d9cfaa6eddd268a89a3dc7f529eb5..6c5fbedf04e1f0785175002333943ab5e6c24e0c 100644
--- a/chrome/browser/extensions/settings/settings_frontend.cc
+++ b/chrome/browser/extensions/settings/settings_frontend.cc
@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/file_path.h"
+#include "base/string_number_conversions.h"
 #include "chrome/browser/extensions/extension_event_names.h"
 #include "chrome/browser/extensions/extension_event_router.h"
 #include "chrome/browser/extensions/extension_service.h"
@@ -14,6 +15,7 @@
 #include "chrome/browser/extensions/settings/settings_leveldb_storage.h"
 #include "chrome/browser/extensions/settings/weak_unlimited_settings_storage.h"
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/common/extensions/api/extension_api.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_service.h"
 
@@ -23,29 +25,6 @@ namespace extensions {
 
 namespace {
 
-const SettingsStorageQuotaEnforcer::Limits kSyncQuota = {
-  // 100K should be enough for simple use, but this can be increased as demand
-  // increases.
-  100 * 1024,
-
-  // Sync supports 5k per settings, so be a bit more restrictive than that.
-  2048,
-
-  // Keep low for sync.
-  512
-};
-
-const SettingsStorageQuotaEnforcer::Limits kLocalQuota = {
-  // Same as localStorage (5MB).
-  5 * 1000 * 1024,
-
-  // No need to be restrictive per key here.
-  UINT_MAX,
-
-  // Ditto.
-  UINT_MAX
-};
-
 // Settings change Observer which forwards changes on to the extension
 // processes for |profile| and its incognito partner if it exists.
 class DefaultObserver : public SettingsObserver {
@@ -109,6 +88,40 @@ void CallbackWithUnlimitedStorage(
   callback.Run(&unlimited_storage);
 }
 
+// Returns the integer at |path| in |dict| as a size_t, or a default value if
+// there's nothing found at that path.
+size_t GetStringAsInteger(
+    const DictionaryValue& dict, const std::string& path, size_t default_size) {
+  std::string as_string;
+  if (!dict.GetString(path, &as_string))
+    return default_size;
+  size_t as_integer = default_size;
+  CHECK(base::StringToSizeT(as_string, &as_integer));
+  return as_integer;
+}
+
+// Constructs a |Limits| configuration by looking up the QUOTA_BYTES,
+// QUOTA_BYTES_PER_ITEM, and MAX_ITEMS properties of a storage area defined
+// in chrome/common/extensions/api/storage.json (via ExtensionAPI).
+SettingsStorageQuotaEnforcer::Limits GetLimitsFromExtensionAPI(
+    const std::string& storage_area_id) {
+  const DictionaryValue* storage_schema =
+      ExtensionAPI::GetInstance()->GetSchema("storage");
+  CHECK(storage_schema);
+
+  DictionaryValue* properties = NULL;
+  storage_schema->GetDictionary(
+      "properties." + storage_area_id + ".properties", &properties);
+  CHECK(properties);
+
+  SettingsStorageQuotaEnforcer::Limits limits = {
+    GetStringAsInteger(*properties, "QUOTA_BYTES.value", UINT_MAX),
+    GetStringAsInteger(*properties, "QUOTA_BYTES_PER_ITEM.value", UINT_MAX),
+    GetStringAsInteger(*properties, "MAX_ITEMS.value", UINT_MAX),
+  };
+  return limits;
+}
+
 }  // namespace
 
 // Ref-counted container for a SettingsBackend object.
@@ -188,7 +201,7 @@ class SettingsFrontend::BackendWrapper
 
   // Only need these until |backend_| exists.
   scoped_refptr<SettingsStorageFactory> storage_factory_;
-  const SettingsStorageQuotaEnforcer::Limits& quota_;
+  const SettingsStorageQuotaEnforcer::Limits quota_;
   scoped_refptr<SettingsObserverList> observers_;
 
   // Wrapped Backend.  Used exclusively on the FILE thread, and is created on
@@ -214,7 +227,9 @@ SettingsFrontend* SettingsFrontend::Create(
 
 SettingsFrontend::SettingsFrontend(
     const scoped_refptr<SettingsStorageFactory>& factory, Profile* profile)
-    : profile_(profile),
+    : local_quota_limit_(GetLimitsFromExtensionAPI("local")),
+      sync_quota_limit_(GetLimitsFromExtensionAPI("sync")),
+      profile_(profile),
       observers_(new SettingsObserverList()),
       profile_observer_(new DefaultObserver(profile)) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
@@ -226,28 +241,28 @@ SettingsFrontend::SettingsFrontend(
   backends_[settings_namespace::LOCAL].app =
       BackendWrapper::CreateAndInit(
           factory,
-          kLocalQuota,
+          local_quota_limit_,
           observers_,
           profile_path.AppendASCII(
               ExtensionService::kLocalAppSettingsDirectoryName));
   backends_[settings_namespace::LOCAL].extension =
       BackendWrapper::CreateAndInit(
           factory,
-          kLocalQuota,
+          local_quota_limit_,
           observers_,
           profile_path.AppendASCII(
               ExtensionService::kLocalExtensionSettingsDirectoryName));
   backends_[settings_namespace::SYNC].app =
       BackendWrapper::CreateAndInit(
           factory,
-          kSyncQuota,
+          sync_quota_limit_,
           observers_,
           profile_path.AppendASCII(
               ExtensionService::kSyncAppSettingsDirectoryName));
   backends_[settings_namespace::SYNC].extension =
       BackendWrapper::CreateAndInit(
           factory,
-          kSyncQuota,
+          sync_quota_limit_,
           observers_,
           profile_path.AppendASCII(
               ExtensionService::kSyncExtensionSettingsDirectoryName));