Avoid useless SYNC_CYCLE_CONTINUATION sync cycle

chrome/browser/sync/sessions/sync_session.cc

Index: chrome/browser/sync/sessions/sync_session.cc
diff --git a/chrome/browser/sync/sessions/sync_session.cc b/chrome/browser/sync/sessions/sync_session.cc
index 064fef6744e9d753fbb4b2e58975646e16ab9190..fe164e468120a702326ee7aa0d06f462e7f71678 100644
--- a/chrome/browser/sync/sessions/sync_session.cc
+++ b/chrome/browser/sync/sessions/sync_session.cc
@@ -233,6 +233,83 @@ std::set<ModelSafeGroup>
   return enabled_groups_with_verified_updates;
 }
 
+namespace {
+// Returns true if the result indicates an error that might go away on its own.
+// In other words, it wouldn't be a bad idea to retry with exponential backoff
+// if we detect one of these errors.
+bool IsTransientError(SyncerError error) {
+  switch (error) {
+    // No operation was not attempted.
+    case UNINITIALIZED:
+      return false;
+
+    // Client-side error.
+    case DIRECTORY_LOOKUP_FAILED:
+      return false;
+
+    // Probably temporary network issues.
+    case NETWORK_CONNECTION_UNAVAILABLE:
+    case NETWORK_IO_ERROR:
+      return true;
+
+    // Error cause is ambiguous.  It's best not to retry in these cases.
+    case SYNC_SERVER_ERROR:
+    case SERVER_RETURN_UNKNOWN_ERROR:
+      return false;
+
+    // These require user intervention
+    case SYNC_AUTH_ERROR:
+    case SERVER_RETURN_INVALID_CREDENTIAL:
+      return false;
+
+    // We have special logic to handle backoff in this case.
+    case SERVER_RETURN_THROTTLED:
+      return false;
+
+    // The server wants us to retry.
+    case SERVER_RETURN_TRANSIENT_ERROR:
+      return true;
+
+    // Handled separately.
+    case SERVER_RETURN_MIGRATION_DONE:
+    case SERVER_RETURN_CLEAR_PENDING:
+    case SERVER_RETURN_NOT_MY_BIRTHDAY:
+    case SERVER_RESPONSE_VALIDATION_FAILED:
+      return false;
+
+    case NO_ERROR:
+      return false;
+  }
+}
+}  // namespace
+
+bool SyncSession::ExperiencedTransientError() const {
+  return IsTransientError(status_controller_->error().download_updates_result)
+      || IsTransientError(status_controller_->error().post_commit_result)
+      || IsTransientError(
+          status_controller_->error().process_commit_response_result);
+}
+
+namespace {
+// Return true if the command in question was attempted and did not complete
+// successfully.
+//
+bool IsError(SyncerError error) {
+  return error != UNINITIALIZED && error != NO_ERROR;
+}
+}  // namespace
+
+bool SyncSession::Succeeded() const {
+  bool download_updates_error =
+      IsError(status_controller_->error().download_updates_result);
+  bool post_commit_error =
+      IsError(status_controller_->error().post_commit_result);
+  bool process_commit_response_error =
+      IsError(status_controller_->error().process_commit_response_result);
+  return !download_updates_error
+      && !post_commit_error
+      && !process_commit_response_error;
+}
 
 }  // namespace sessions
 }  // namespace browser_sync