[fsp] Add support for observing entries and notifying about changes.

chrome/browser/chromeos/file_system_provider/fake_provided_file_system.cc

Index: chrome/browser/chromeos/file_system_provider/fake_provided_file_system.cc
diff --git a/chrome/browser/chromeos/file_system_provider/fake_provided_file_system.cc b/chrome/browser/chromeos/file_system_provider/fake_provided_file_system.cc
index b33477477c586e6c6d91e7a70ce2f437150fcae5..ade1d7bd37f2d38563bb5d1823d537a13abf90a5 100644
--- a/chrome/browser/chromeos/file_system_provider/fake_provided_file_system.cc
+++ b/chrome/browser/chromeos/file_system_provider/fake_provided_file_system.cc
@@ -331,6 +331,21 @@ RequestManager* FakeProvidedFileSystem::GetRequestManager() {
   return NULL;
 }
 
+void FakeProvidedFileSystem::AddObserver(Observer* observer) {
+  DCHECK(observer);
+  observers_.AddObserver(observer);
+}
+
+void FakeProvidedFileSystem::RemoveObserver(Observer* observer) {
+  DCHECK(observer);
+  observers_.RemoveObserver(observer);
+}
+
+ObserverList<ProvidedFileSystemInterface::Observer>*
+FakeProvidedFileSystem::GetObservers() {
+  return &observers_;
+}
+
 ProvidedFileSystemInterface* FakeProvidedFileSystem::Create(
     Profile* profile,
     const ProvidedFileSystemInfo& file_system_info) {