Revert of Remove DCHECK_IMPLIES/CHECK_IMPLIES.

cc/output/direct_renderer.cc

 // Copyright 2012 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/output/direct_renderer.h"
 
 #include <utility>
 #include <vector>
 
 #include "base/containers/hash_tables.h"
@@ skipping 418 matching lines @@
   bool is_root_render_pass =
       frame->current_render_pass == frame->root_render_pass;
   bool has_external_stencil_test =
       is_root_render_pass && output_surface_->HasExternalStencilTest();
   bool should_clear_surface =
       !has_external_stencil_test &&
       (!is_root_render_pass || settings_->should_clear_root_render_pass);
 
   // If |has_external_stencil_test| we can't discard or clear. Make sure we
   // don't need to.
-  DCHECK(!has_external_stencil_test ||
-         !frame->current_render_pass->has_transparent_background);
+  DCHECK_IMPLIES(has_external_stencil_test,
+                 !frame->current_render_pass->has_transparent_background);
 
   SurfaceInitializationMode mode;
   if (should_clear_surface && render_pass_is_clipped) {
     mode = SURFACE_INITIALIZATION_MODE_SCISSORED_CLEAR;
   } else if (should_clear_surface) {
     mode = SURFACE_INITIALIZATION_MODE_FULL_SURFACE_CLEAR;
   } else {
     mode = SURFACE_INITIALIZATION_MODE_PRESERVE;
   }
 
@@ skipping 84 matching lines @@
   ScopedResource* texture = render_pass_textures_.get(id);
   return texture && texture->id();
 }
 
 // static
 gfx::Size DirectRenderer::RenderPassTextureSize(const RenderPass* render_pass) {
   return render_pass->output_rect.size();
 }
 
 }  // namespace cc