[Sync] Implement encryption-aware conflict resolution.

chrome/browser/sync/engine/conflict_resolver.h

 // 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.
 //
 // A class that watches the syncer and attempts to resolve any conflicts that
 // occur.
 
 #ifndef CHROME_BROWSER_SYNC_ENGINE_CONFLICT_RESOLVER_H_
 #define CHROME_BROWSER_SYNC_ENGINE_CONFLICT_RESOLVER_H_
 #pragma once
@@ skipping 21 matching lines @@
 namespace sessions {
 class ConflictProgress;
 class StatusController;
 }  // namespace sessions
 
 class ConflictResolver {
   friend class SyncerTest;
   FRIEND_TEST_ALL_PREFIXES(SyncerTest,
                            ConflictResolverMergeOverwritesLocalEntry);
  public:
+  // Enumeration of different conflict resolutions. Used for histogramming.
+  enum SimpleConflictResolutions {
+    OVERWRITE_LOCAL,           // Resolved by overwriting local changes.
+    OVERWRITE_SERVER,          // Resolved by overwriting server changes.
+    UNDELETE,                  // Resolved by undeleting local item.
+    IGNORE_ENCRYPTION,         // Resolved by ignoring an encryption-only server
+                               // change.
+    NIGORI_MERGE,              // Resolved by merging nigori nodes.
+    CHANGES_MATCH,             // Resolved by ignoring both local and server
+                               // changes because they matched.
+    CONFLICT_RESOLUTION_SIZE,
+  };
+
   ConflictResolver();
   ~ConflictResolver();
   // Called by the syncer at the end of a update/commit cycle.
   // Returns true if the syncer should try to apply its updates again.
   bool ResolveConflicts(const syncable::ScopedDirLookup& dir,
                         const sessions::ConflictProgress& progress,
                         sessions::StatusController* status);
 
  private:
   // We keep a map to record how often we've seen each conflict set. We use this
@@ skipping 40 matching lines @@
 
   ConflictSetCountMap conflict_set_count_map_;
   SimpleConflictCountMap simple_conflict_count_map_;
 
   DISALLOW_COPY_AND_ASSIGN(ConflictResolver);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_ENGINE_CONFLICT_RESOLVER_H_