Add SNAPSHOT sync mode to LocalFileSyncContext::PrepareForSync

chrome/browser/sync_file_system/local/canned_syncable_file_system.cc

Index: chrome/browser/sync_file_system/local/canned_syncable_file_system.cc
diff --git a/chrome/browser/sync_file_system/local/canned_syncable_file_system.cc b/chrome/browser/sync_file_system/local/canned_syncable_file_system.cc
index d1d4e6a9f4f40aa6b9da7a71ad882d54f38cb1ea..d17f1592ec0bea25c5af9f94581d754e05fc0d0c 100644
--- a/chrome/browser/sync_file_system/local/canned_syncable_file_system.cc
+++ b/chrome/browser/sync_file_system/local/canned_syncable_file_system.cc
@@ -15,6 +15,7 @@
 #include "base/run_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "base/task_runner_util.h"
+#include "chrome/browser/sync_file_system/file_change.h"
 #include "chrome/browser/sync_file_system/local/local_file_change_tracker.h"
 #include "chrome/browser/sync_file_system/local/local_file_sync_context.h"
 #include "chrome/browser/sync_file_system/local/sync_file_system_backend.h"
@@ -498,7 +499,7 @@ quota::QuotaStatusCode CannedSyncableFileSystem::GetUsageAndQuota(
 
 void CannedSyncableFileSystem::GetChangedURLsInTracker(
     FileSystemURLSet* urls) {
-  return RunOnThread(
+  RunOnThread(
       file_task_runner_.get(),
       FROM_HERE,
       base::Bind(&LocalFileChangeTracker::GetAllChangedURLs,
@@ -508,7 +509,7 @@ void CannedSyncableFileSystem::GetChangedURLsInTracker(
 
 void CannedSyncableFileSystem::ClearChangeForURLInTracker(
     const FileSystemURL& url) {
-  return RunOnThread(
+  RunOnThread(
       file_task_runner_.get(),
       FROM_HERE,
       base::Bind(&LocalFileChangeTracker::ClearChangesForURL,
@@ -516,6 +517,17 @@ void CannedSyncableFileSystem::ClearChangeForURLInTracker(
                  url));
 }
 
+void CannedSyncableFileSystem::GetChangesForURLInTracker(
+    const FileSystemURL& url,
+    FileChangeList* changes) {
+  RunOnThread(
+      file_task_runner_.get(),
+      FROM_HERE,
+      base::Bind(&LocalFileChangeTracker::GetChangesForURL,
+                 base::Unretained(backend()->change_tracker()),
+                 url, changes));
+}
+
 SyncFileSystemBackend* CannedSyncableFileSystem::backend() {
   return SyncFileSystemBackend::GetBackend(file_system_context_);
 }