gfx: Use unsigned strides for gpu memory buffers.

cc/raster/one_copy_raster_buffer_provider.cc

 // Copyright 2014 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/raster/one_copy_raster_buffer_provider.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <limits>
@@ skipping 232 matching lines @@
                            client_name),
         100.0f * fraction_saved);
   }
 
   if (staging_buffer->gpu_memory_buffer) {
     gfx::GpuMemoryBuffer* buffer = staging_buffer->gpu_memory_buffer.get();
     DCHECK_EQ(1u, gfx::NumberOfPlanesForBufferFormat(buffer->GetFormat()));
     bool rv = buffer->Map();
     DCHECK(rv);
     DCHECK(buffer->memory(0));
-    // RasterBufferProvider::PlaybackToMemory only supports unsigned strides.
-    DCHECK_GE(buffer->stride(0), 0);
 
     DCHECK(!playback_rect.IsEmpty())
         << "Why are we rastering a tile that's not dirty?";
     RasterBufferProvider::PlaybackToMemory(
         buffer->memory(0), resource->format(), staging_buffer->size,
         buffer->stride(0), raster_source, raster_full_rect, playback_rect,
         scale, playback_settings);
     buffer->Unmap();
     staging_buffer->content_id = new_content_id;
   }
@@ skipping 115 matching lines @@
   resource_lock->set_synchronized(!async_worker_context_enabled_);
 }
 
 gfx::BufferUsage OneCopyRasterBufferProvider::StagingBufferUsage() const {
   return use_partial_raster_
              ? gfx::BufferUsage::GPU_READ_CPU_READ_WRITE_PERSISTENT
              : gfx::BufferUsage::GPU_READ_CPU_READ_WRITE;
 }
 
 }  // namespace cc