Add a skeleton of idle time spell checker

third_party/WebKit/Source/core/editing/spellcheck/IdleSpellCheckCallback.h

+// 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.
+
+#ifndef IdleSpellCheckCallback_h
+#define IdleSpellCheckCallback_h
+
+#include "core/dom/IdleRequestCallback.h"
+#include "core/frame/LocalFrame.h"
+#include "platform/Timer.h"
+
+namespace blink {
+
+// Main class for the implementation of idle time spell checker.
+class IdleSpellCheckCallback final : public IdleRequestCallback {
+ public:
+  // TODO(xiaochengh): Make each LocalFrame own an IdleSpellCheckCallback.
+  static IdleSpellCheckCallback* create(LocalFrame&);
+  ~IdleSpellCheckCallback() override;
+
+  // Transit to HotModeRequested, if possible. Called by operations that need
+  // spell checker to follow up.
+  // TODO(xiaochengh): Add proper call sites.
+  void setNeedsHotModeInvocation();
+
+  // Transit to ColdModeTimerStarted, if possible. Sets up a timer, and requests
+  // cold mode invocation if no critical operation occurs before timer firing.
+  // TODO(xiaochengh): Add proper call sites.
+  void setNeedsColdModeInvocation();
+
+  // Cleans everything up and makes the callback inactive. Should be called when
+  // document is detached or spellchecking is globally disabled.
+  // TODO(xiaochengh): Add proper call sites.
+  void deactivate();
+
+  DECLARE_VIRTUAL_TRACE();
+
+ private:
+  explicit IdleSpellCheckCallback(LocalFrame&);
+  void handleEvent(IdleDeadline*) override;
+
+  LocalFrame& frame() const { return *m_frame; }
+
+  enum class State {
+    kInactive,
+    kHotModeRequested,
+    kInHotModeInvocation,
+    kColdModeTimerStarted,
+    kColdModeRequested,
+    kInColdModeInvocation
+  };
+
+  // Returns whether spell checking is globally enabled.
+  bool isSpellCheckingEnabled() const;
+
+  // Calls requestIdleCallback with this IdleSpellCheckCallback.
+  void requestInvocation();
+
+  // Functions for hot mode.
+  void hotModeInvocation(IdleDeadline*);
+
+  // Functions for cold mode.
+  void coldModeTimerFired(TimerBase*);
+  void coldModeInvocation(IdleDeadline*);
+  bool coldModeFinishesFullDocument() const;
+
+  State m_state;
+  const Member<LocalFrame> m_frame;
+
+  // TODO(xiaochengh): assign the timer to some proper task runner.
+  Timer<IdleSpellCheckCallback> m_coldModeTimer;
+};
+
+}  // namespace blink
+
+#endif  // IdleSpellCheckCallback_h