SnapshotController implementation. It will be used in WebContentsObservers for Offline Pages - to d…

components/offline_pages/snapshot_controller.cc

+// Copyright 2016 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.
+
+#include "components/offline_pages/snapshot_controller.h"
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/logging.h"
+#include "base/time/time.h"
+
+namespace {
+// Delay, in milliseconds, between the main document parsed event and snapshot.
+// Note if the "load" event fires before this delay is up, then the snapshot
+// is taken immediately.
+const size_t DELAY_AFTER_DOCUMENT_AVAILABLE = 7000;

[fgorski, 2016/04/26 02:45:57]

kDelayAfterDocumentAvailable  -- I believe style guide mandates that for C++

+
+}  // namespace
+
+namespace offline_pages {
+
+SnapshotController::SnapshotController(
+    const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
+    SnapshotController::Client* client)
+    : task_runner_(task_runner),
+      client_(client),
+      state_(State::kReady),
+      weak_ptr_factory_(this) {
+}
+
+SnapshotController::~SnapshotController() {}
+
+void SnapshotController::Reset() {
+  state_ = State::kReady;
+}
+
+void SnapshotController::Stop() {
+  state_ = State::kStopped;
+}
+
+void SnapshotController::PendingSnapshotCompleted() {
+  // Unless the controller is "stopped", enable the subsequent snapshots.
+  // Stopped state prevents any further snapshots form being started.
+  if (state_ == State::kStopped)
+    return;
+  DCHECK(state_ == State::kSnapshotPending);
+  state_ = State::kReady;
+}
+
+void SnapshotController::DocumentAvailableInMainFrame() {
+  // Post a delayed task. The snapshot will happen either when the delay
+  // is up, or if the "load" event is dispatched in the main frame.
+  task_runner_->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&SnapshotController::MaybeStartSnapshot,
+                 weak_ptr_factory_.GetWeakPtr()),
+      base::TimeDelta::FromMilliseconds(DELAY_AFTER_DOCUMENT_AVAILABLE));
+}
+
+void SnapshotController::DocumentOnLoadCompletedInMainFrame() {
+  MaybeStartSnapshot();
+  // No more snapshots after onLoad (there still can be other events
+  // or delayed tasks that can try to start another snapshot)
+  Stop();
+}
+
+void SnapshotController::MaybeStartSnapshot() {
+  if (state_ != State::kReady)
+    return;
+  if (client_->StartSnapshot())
+    state_ = State::kSnapshotPending;
+}
+
+size_t SnapshotController::GetDelayAfterDocumentAvailableForTest() {
+  return DELAY_AFTER_DOCUMENT_AVAILABLE;
+}
+
+
+}  // namespace offline_pages