Revert of Remove DCHECK_IMPLIES/CHECK_IMPLIES.

cc/layers/picture_layer_impl_unittest.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 "cc/layers/picture_layer_impl.h"
 
 #include <algorithm>
 #include <limits>
 #include <set>
 #include <utility>
@@ skipping 214 matching lines @@
     host_impl_.CreatePendingTree();
     host_impl_.pending_tree()->PushPageScaleFromMainThread(1.f, 0.00001f,
                                                            100000.f);
     LayerTreeImpl* pending_tree = host_impl_.pending_tree();
     pending_tree->SetDeviceScaleFactor(
         host_impl_.active_tree()->device_scale_factor());
 
     // Steal from the recycled tree if possible.
     scoped_ptr<LayerImpl> pending_root = pending_tree->DetachLayerTree();
     scoped_ptr<FakePictureLayerImpl> pending_layer;
-    DCHECK(!pending_root || pending_root->id() == root_id_);
+    DCHECK_IMPLIES(pending_root, pending_root->id() == root_id_);
     if (!pending_root) {
       pending_root = LayerImpl::Create(pending_tree, root_id_);
       pending_layer = FakePictureLayerImpl::Create(pending_tree, id_);
       if (!tile_size.IsEmpty())
         pending_layer->set_fixed_tile_size(tile_size);
       pending_layer->SetDrawsContent(true);
     } else {
       pending_layer.reset(static_cast<FakePictureLayerImpl*>(
           pending_root->RemoveChild(pending_root->children()[0]).release()));
       if (!tile_size.IsEmpty())
@@ skipping 4780 matching lines @@
   // New low res tiling.
   EXPECT_TRUE(tilings->tiling_at(2)->may_contain_low_resolution_tiles());
 
   // This tiling will be high res now, it won't contain low res content since it
   // was all destroyed.
   EXPECT_FALSE(tilings->tiling_at(1)->may_contain_low_resolution_tiles());
 }
 
 }  // namespace
 }  // namespace cc