Revert of Remove DCHECK_IMPLIES/CHECK_IMPLIES.

content/renderer/input/input_handler_proxy.cc

 // Copyright 2013 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 "content/renderer/input/input_handler_proxy.h"
 
 #include <algorithm>
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
@@ skipping 739 matching lines @@
                        "InputHandlerProxy::ExtendBoostedFlingTimeout",
                        TRACE_EVENT_SCOPE_THREAD);
   deferred_fling_cancel_time_seconds_ =
       event.timeStampSeconds + kFlingBoostTimeoutDelaySeconds;
   last_fling_boost_event_ = event;
 }
 
 void InputHandlerProxy::Animate(base::TimeTicks time) {
   // If using synchronous animate, then only expect Animate attempts started by
   // the synchronous system. Don't let the InputHandler try to Animate also.
-  DCHECK(!input_handler_->IsCurrentlyScrollingInnerViewport() ||
-         allow_root_animate_);
+  DCHECK_IMPLIES(input_handler_->IsCurrentlyScrollingInnerViewport(),
+                 allow_root_animate_);
 
   if (scroll_elasticity_controller_)
     scroll_elasticity_controller_->Animate(time);
 
   if (!fling_curve_)
     return;
 
   last_fling_animate_time_ = time;
   double monotonic_time_sec = InSecondsF(time);
 
@@ skipping 267 matching lines @@
   // trigger a scroll, e.g., with a trivial time delta between fling updates.
   // Return true in this case to prevent early fling termination.
   if (std::abs(clipped_increment.width) < kScrollEpsilon &&
       std::abs(clipped_increment.height) < kScrollEpsilon)
     return true;
 
   return did_scroll;
 }
 
 }  // namespace content