gfx: Use unsigned strides for gpu memory buffers.

cc/raster/zero_copy_raster_buffer_provider.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/raster/zero_copy_raster_buffer_provider.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 
@@ skipping 28 matching lines @@
     TRACE_EVENT0("cc", "ZeroCopyRasterBuffer::Playback");
     gfx::GpuMemoryBuffer* buffer = lock_.GetGpuMemoryBuffer();
     if (!buffer)
       return;
 
     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);
 
     // TODO(danakj): Implement partial raster with raster_dirty_rect.
     RasterBufferProvider::PlaybackToMemory(
         buffer->memory(0), resource_->format(), resource_->size(),
         buffer->stride(0), raster_source, raster_full_rect, raster_full_rect,
         scale, playback_settings);
     buffer->Unmap();
   }
 
  private:
@@ skipping 57 matching lines @@
 }
 
 bool ZeroCopyRasterBufferProvider::CanPartialRasterIntoProvidedResource()
     const {
   return false;
 }
 
 void ZeroCopyRasterBufferProvider::Shutdown() {}
 
 }  // namespace cc