Fix recursive FilePathWatcher on Linux when touching a directory

FilePathWatcher is DCHECKing when touching a directory for a recursive
directory, this is due to invariant being broken between members:
|recursive_paths_by_watch_| and |recursive_watches_by_path_|. Function
UpdateRecursiveWatches() was erasing from |recursive_watches_by_path_|,
but wasn't erasing from |recursive_paths_by_watch_|.

This CL fixes UpdateRecursiveWatches() to maintain the invariant, by
erasing from |recursive_paths_by_watch_| too.

Test: base_unittests --gtest_filter="*RecursiveWatch*"
Bug: 995196
Change-Id: Ibcc8b015d7d9b68d2eff59f4ae9e87d84d76991f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1757960Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Luciano Pacheco <lucmult@chromium.org>
Auto-Submit: Luciano Pacheco <lucmult@chromium.org>
Cr-Commit-Position: refs/heads/master@{#688430}

base/files/file_path_watcher_linux.cc

@@ -629,6 +629,9 @@ void FilePathWatcherImpl::UpdateRecursiveWatches(
       break;
     if (!DirectoryExists(cur_path))
       g_inotify_reader.Get().RemoveWatch(end_it->second, this);
+
+    // Keep it in sync with |recursive_watches_by_path_| crbug.com/995196.
+    recursive_paths_by_watch_.erase(end_it->second);
   }
   recursive_watches_by_path_.erase(start_it, end_it);
   UpdateRecursiveWatchesForPath(changed_dir);

base/files/file_path_watcher_unittest.cc

@@ -501,6 +501,16 @@ TEST_F(FilePathWatcherTest, RecursiveWatch) {
   ASSERT_TRUE(base::CreateDirectory(subdir));
   ASSERT_TRUE(WaitForEvents());
 
+// Mac and Win don't generate events for Touch.
+// Android TouchFile returns false.
+#if !(defined(OS_MACOSX) || defined(OS_WIN) || defined(OS_ANDROID))
+  // Touch "$dir".
+  Time access_time;
+  ASSERT_TRUE(Time::FromString("Wed, 16 Nov 1994, 00:00:00", &access_time));
+  ASSERT_TRUE(base::TouchFile(dir, access_time, access_time));
+  ASSERT_TRUE(WaitForEvents());
+#endif  // !(defined(OS_MACOSX) || defined(OS_WIN) || defined(OS_ANDROID))
+
   // Create "$dir/subdir/subdir_file1".
   FilePath subdir_file1(subdir.AppendASCII("subdir_file1"));
   ASSERT_TRUE(WriteFile(subdir_file1, "content"));