Revert of Remove DCHECK_IMPLIES/CHECK_IMPLIES.

cc/scheduler/scheduler.cc

 // Copyright 2011 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 "cc/scheduler/scheduler.h"
 
 #include <algorithm>
 
 #include "base/auto_reset.h"
 #include "base/logging.h"
@@ skipping 57 matching lines @@
       begin_impl_frame_deadline_mode_(
           SchedulerStateMachine::BEGIN_IMPL_FRAME_DEADLINE_MODE_NONE),
       begin_impl_frame_tracker_(BEGINFRAMETRACKER_FROM_HERE),
       state_machine_(settings),
       inside_process_scheduled_actions_(false),
       inside_action_(SchedulerStateMachine::ACTION_NONE),
       weak_factory_(this) {
   TRACE_EVENT1("cc", "Scheduler::Scheduler", "settings", settings_.AsValue());
   DCHECK(client_);
   DCHECK(!state_machine_.BeginFrameNeeded());
-  DCHECK(!settings_.use_external_begin_frame_source || external_frame_source_);
-  DCHECK(settings_.use_external_begin_frame_source || synthetic_frame_source_);
+  DCHECK_IMPLIES(settings_.use_external_begin_frame_source,
+                 external_frame_source_);
+  DCHECK_IMPLIES(!settings_.use_external_begin_frame_source,
+                 synthetic_frame_source_);
   DCHECK(unthrottled_frame_source_);
 
   begin_retro_frame_closure_ =
       base::Bind(&Scheduler::BeginRetroFrame, weak_factory_.GetWeakPtr());
   begin_impl_frame_deadline_closure_ = base::Bind(
       &Scheduler::OnBeginImplFrameDeadline, weak_factory_.GetWeakPtr());
 
   frame_source_->AddObserver(this);
   frame_source_->AddSource(primary_frame_source());
   primary_frame_source()->SetClientReady();
@@ skipping 747 matching lines @@
 }
 
 bool Scheduler::IsBeginMainFrameSentOrStarted() const {
   return (state_machine_.begin_main_frame_state() ==
               SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT ||
           state_machine_.begin_main_frame_state() ==
               SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_STARTED);
 }
 
 }  // namespace cc