Revert of cc: Remove tile sharing from tilings.

cc/base/tiling_data.cc

 // Copyright 2010 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/base/tiling_data.h"
 
 #include <algorithm>
 
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/vector2d.h"
@@ skipping 400 matching lines @@
 
 bool TilingData::BaseDifferenceIterator::HasConsiderRect() const {
   // Consider indices are either all valid or all equal to -1.
   DCHECK((0 <= consider_left_ && consider_left_ <= consider_right_ &&
           0 <= consider_top_ && consider_top_ <= consider_bottom_) ||
          (consider_left_ == -1 && consider_top_ == -1 &&
           consider_right_ == -1 && consider_bottom_ == -1));
   return consider_left_ != -1;
 }
 
-TilingData::DifferenceIterator::DifferenceIterator() {
-}
-
 TilingData::DifferenceIterator::DifferenceIterator(
     const TilingData* tiling_data,
     const gfx::Rect& consider_rect,
     const gfx::Rect& ignore_rect)
     : BaseDifferenceIterator(tiling_data, consider_rect, ignore_rect) {
   if (!HasConsiderRect()) {
     done();
     return;
   }
 
@@ skipping 424 matching lines @@
 
     // We should always end up in an around rect at some point.
     // Since the direction is now vertical, we have to ensure that we will
     // advance.
     DCHECK_GE(horizontal_step_count_, 1);
     DCHECK_GE(vertical_step_count_, 1);
   }
 }
 
 }  // namespace cc