Fix file path notification filtering on Windows.

base/files/file_path_watcher_win.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/files/file_path_watcher.h"
 
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "base/files/file.h"
 #include "base/files/file_path.h"
@@ skipping 79 matching lines @@
                                 bool recursive,
                                 const FilePathWatcher::Callback& callback) {
   DCHECK(target_.value().empty());  // Can only watch one path.
 
   set_message_loop(MessageLoopProxy::current());
   callback_ = callback;
   target_ = path;
   recursive_watch_ = recursive;
   MessageLoop::current()->AddDestructionObserver(this);
 
+  File::Info file_info;
+  if (GetFileInfo(target_, &file_info)) {
+    last_modified_ = file_info.last_modified;
+    first_notification_ = Time::Now();
+  }
+
   if (!UpdateWatch())
     return false;
 
   watcher_.StartWatching(handle_, this);
 
   return true;
 }
 
 void FilePathWatcherImpl::Cancel() {
   if (callback_.is_null()) {
@@ skipping 34 matching lines @@
   scoped_refptr<FilePathWatcherImpl> keep_alive(this);
 
   if (!UpdateWatch()) {
     callback_.Run(target_, true /* error */);
     return;
   }
 
   // Check whether the event applies to |target_| and notify the callback.
   File::Info file_info;
   bool file_exists = GetFileInfo(target_, &file_info);
-  if (file_exists && (last_modified_.is_null() ||
-      last_modified_ != file_info.last_modified)) {
+  if (recursive_watch_) {
+    // Only the mtime of |target_| is tracked but in a recursive watch,
+    // some other file or directory may have changed so all notifications
+    // are passed through. It is possible to figure out which file changed
+    // using ReadDirectoryChangesW() instead of FindFirstChangeNotification(),
+    // but that function is quite complicated:
+    // http://qualapps.blogspot.com/2010/05/understanding-readdirectorychangesw.html
+    callback_.Run(target_, false);
+  } else if (file_exists && (last_modified_.is_null() ||
+             last_modified_ != file_info.last_modified)) {
     last_modified_ = file_info.last_modified;
     first_notification_ = Time::Now();
     callback_.Run(target_, false);
-  } else if (file_exists && !first_notification_.is_null()) {
+  } else if (file_exists && last_modified_ == file_info.last_modified &&
+             !first_notification_.is_null()) {
     // The target's last modification time is equal to what's on record. This
     // means that either an unrelated event occurred, or the target changed
     // again (file modification times only have a resolution of 1s). Comparing
     // file modification times against the wall clock is not reliable to find
     // out whether the change is recent, since this code might just run too
     // late. Moreover, there's no guarantee that file modification time and wall
     // clock times come from the same source.
     //
     // Instead, the time at which the first notification carrying the current
     // |last_notified_| time stamp is recorded. Later notifications that find
@@ skipping 53 matching lines @@
     return false;
   }
 
   return true;
 }
 
 bool FilePathWatcherImpl::UpdateWatch() {
   if (handle_ != INVALID_HANDLE_VALUE)
     DestroyWatch();
 
-  File::Info file_info;
-  if (GetFileInfo(target_, &file_info)) {
-    last_modified_ = file_info.last_modified;
-    first_notification_ = Time::Now();
-  }
-
   // Start at the target and walk up the directory chain until we succesfully
   // create a watch handle in |handle_|. |child_dirs| keeps a stack of child
   // directories stripped from target, in reverse order.
   std::vector<FilePath> child_dirs;
   FilePath watched_path(target_);
   while (true) {
     if (!SetupWatchHandle(watched_path, recursive_watch_, &handle_))
       return false;
 
     // Break if a valid handle is returned. Try the parent directory otherwise.
@@ skipping 34 matching lines @@
   handle_ = INVALID_HANDLE_VALUE;
 }
 
 }  // namespace
 
 FilePathWatcher::FilePathWatcher() {
   impl_ = new FilePathWatcherImpl();
 }
 
 }  // namespace base