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

chrome/browser/extensions/settings/weak_unlimited_settings_storage.cc

Index: chrome/browser/extensions/settings/weak_unlimited_settings_storage.cc
diff --git a/chrome/browser/extensions/settings/weak_unlimited_settings_storage.cc b/chrome/browser/extensions/settings/weak_unlimited_settings_storage.cc
index c1232cbaaa66bad184a8806dba7dfd24fec3462a..3d04ab3c5732370c6b595fc9e6857df48636d2e2 100644
--- a/chrome/browser/extensions/settings/weak_unlimited_settings_storage.cc
+++ b/chrome/browser/extensions/settings/weak_unlimited_settings_storage.cc
@@ -12,6 +12,20 @@ WeakUnlimitedSettingsStorage::WeakUnlimitedSettingsStorage(
 
 WeakUnlimitedSettingsStorage::~WeakUnlimitedSettingsStorage() {}
 
+size_t WeakUnlimitedSettingsStorage::GetBytesInUse(const std::string& key) {
+  return delegate_->GetBytesInUse(key);
+}
+
+size_t WeakUnlimitedSettingsStorage::GetBytesInUse(
+    const std::vector<std::string>& keys) {
+  return delegate_->GetBytesInUse(keys);
+}
+
+
+size_t WeakUnlimitedSettingsStorage::GetBytesInUse() {
+  return delegate_->GetBytesInUse();
+}
+
 SettingsStorage::ReadResult WeakUnlimitedSettingsStorage::Get(
     const std::string& key) {
   return delegate_->Get(key);