Revert of Mojo: Armed Watchers

mojo/edk/system/watch.h

Index: mojo/edk/system/watch.h
diff --git a/mojo/edk/system/watch.h b/mojo/edk/system/watch.h
deleted file mode 100644
index f277de991767d49d95c1239df1f335b3c90ff7c7..0000000000000000000000000000000000000000
--- a/mojo/edk/system/watch.h
+++ /dev/null
@@ -1,124 +0,0 @@
-// Copyright 2017 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 MOJO_EDK_SYSTEM_WATCH_H_
-#define MOJO_EDK_SYSTEM_WATCH_H_
-
-#include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "base/synchronization/lock.h"
-#include "mojo/edk/system/atomic_flag.h"
-#include "mojo/edk/system/handle_signals_state.h"
-
-namespace mojo {
-namespace edk {
-
-class Dispatcher;
-class WatcherDispatcher;
-
-// Encapsulates the state associated with a single watch context within a
-// watcher.
-//
-// Every Watch has its own cancellation state, and is captured by RequestContext
-// notification finalizers to avoid redundant context resolution during
-// finalizer execution.
-class Watch : public base::RefCountedThreadSafe<Watch> {
- public:
-  // Constructs a Watch which represents a watch within |watcher| associated
-  // with |context|, watching |dispatcher| for |signals|.
-  Watch(const scoped_refptr<WatcherDispatcher>& watcher,
-        const scoped_refptr<Dispatcher>& dispatcher,
-        uintptr_t context,
-        MojoHandleSignals signals);
-
-  // Notifies the Watch of a potential state change.
-  //
-  // If |allowed_to_call_callback| is true, this may add a notification
-  // finalizer to the current RequestContext to invoke the watcher's callback
-  // with this watch's context. See return values below.
-  //
-  // This is called directly by WatcherDispatcher whenever the Watch's observed
-  // dispatcher notifies the WatcherDispatcher of a state change.
-  //
-  // Returns |true| if the Watch entered or remains in a ready state as a result
-  // of the state change. If |allowed_to_call_callback| was true in this case,
-  // the Watch will have also attached a notification finalizer to the current
-  // RequestContext.
-  //
-  // Returns |false| if the
-  bool NotifyState(const HandleSignalsState& state,
-                   bool allowed_to_call_callback);
-
-  // Notifies the watch of cancellation ASAP. This will always be the last
-  // notification sent for the watch.
-  void Cancel();
-
-  // Finalizer method for RequestContexts. This method is invoked once for every
-  // notification finalizer added to a RequestContext by this object. This calls
-  // down into the WatcherDispatcher to do the actual notification call.
-  void InvokeCallback(MojoResult result,
-                      const HandleSignalsState& state,
-                      MojoWatcherNotificationFlags flags);
-
-  const scoped_refptr<Dispatcher>& dispatcher() const { return dispatcher_; }
-  uintptr_t context() const { return context_; }
-
-  MojoResult last_known_result() const {
-    AssertWatcherLockAcquired();
-    return last_known_result_;
-  }
-
-  MojoHandleSignalsState last_known_signals_state() const {
-    AssertWatcherLockAcquired();
-    return last_known_signals_state_;
-  }
-
-  bool ready() const {
-    AssertWatcherLockAcquired();
-    return last_known_result_ == MOJO_RESULT_OK ||
-           last_known_result_ == MOJO_RESULT_FAILED_PRECONDITION;
-  }
-
- private:
-  friend class base::RefCountedThreadSafe<Watch>;
-
-  ~Watch();
-
-#if DCHECK_IS_ON()
-  void AssertWatcherLockAcquired() const;
-#else
-  void AssertWatcherLockAcquired() const {}
-#endif
-
-  const scoped_refptr<WatcherDispatcher> watcher_;
-  const scoped_refptr<Dispatcher> dispatcher_;
-  const uintptr_t context_;
-  const MojoHandleSignals signals_;
-
-  // The result code with which this Watch would notify if currently armed,
-  // based on the last known signaling state of |dispatcher_|. Guarded by the
-  // owning WatcherDispatcher's lock.
-  MojoResult last_known_result_ = MOJO_RESULT_UNKNOWN;
-
-  // The last known signaling state of |dispatcher_|. Guarded by the owning
-  // WatcherDispatcher's lock.
-  MojoHandleSignalsState last_known_signals_state_ = {0, 0};
-
-  // Guards |is_cancelled_| below and mutually excludes individual watch
-  // notification executions for this same watch context.
-  //
-  // Note that this should only be acquired from a RequestContext finalizer to
-  // ensure that no other internal locks are already held.
-  base::Lock notification_lock_;
-
-  // Guarded by |notification_lock_|.
-  bool is_cancelled_ = false;
-
-  DISALLOW_COPY_AND_ASSIGN(Watch);
-};
-
-}  // namespace edk
-}  // namespace mojo
-
-#endif  // MOJO_EDK_SYSTEM_WATCH_H_