Docserver: Pull knowledge of host file systems into a single

chrome/common/extensions/docs/server2/host_file_system_iterator.py

Index: chrome/common/extensions/docs/server2/host_file_system_iterator.py
diff --git a/chrome/common/extensions/docs/server2/host_file_system_iterator.py b/chrome/common/extensions/docs/server2/host_file_system_iterator.py
index 20c0741c774ffa55f3227194a3eaa4f8fb28cf26..1ecbb48da161b9c34a26c6cc928e80754e3bd981 100644
--- a/chrome/common/extensions/docs/server2/host_file_system_iterator.py
+++ b/chrome/common/extensions/docs/server2/host_file_system_iterator.py
@@ -10,9 +10,8 @@ class HostFileSystemIterator(object):
   ascending (oldest to newest version) and descending order.
   '''
 
-  def __init__(self, file_system_creator, host_file_system, branch_utility):
-    self._file_system_creator = file_system_creator
-    self._host_file_system = host_file_system
+  def __init__(self, file_system_provider, branch_utility):
+    self._file_system_provider = file_system_provider
     self._branch_utility = branch_utility
 
   @memoize
@@ -24,14 +23,8 @@ class HostFileSystemIterator(object):
     at each call of ForEach, but the data isn't going to change between calls.
     Use |branch| to memoize the created file systems.
     '''
-    if branch == 'trunk':
-      # Don't create a new file system for trunk, since there is a bug with the
-      # current architecture and design of HostFileSystemCreator, where
-      # creating 'trunk' ignores the pinned revision (in fact, it bypasses
-      # every difference including whether the file system is patched).
-      # TODO(kalman): Fix HostFileSystemCreator and update this comment.
-      return self._host_file_system
-    return self._file_system_creator.Create(branch)
+    return (self._file_system_provider.GetTrunk() if branch == 'trunk' else
+            self._file_system_provider.GetBranch(branch))
 
   def _ForEach(self, channel_info, callback, get_next):
     '''Iterates through a sequence of file systems defined by |get_next| until