[Ozone-Dri] Replace blend with copy to the modeset buffer

ui/ozone/platform/dri/screen_manager.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 "ui/ozone/platform/dri/screen_manager.h"
 
 #include <xf86drmMode.h>
 
 #include "third_party/skia/include/core/SkCanvas.h"
 #include "ui/gfx/geometry/point.h"
@@ skipping 36 matching lines @@
     return;
   }
 
   // Don't copy anything if the sizes mismatch. This can happen when the user
   // changes modes.
   if (saved_buffer.canvas()->getBaseLayerSize() !=
       modeset_buffer.canvas()->getBaseLayerSize())
     return;
 
   skia::RefPtr<SkImage> image = saved_buffer.image();
-  modeset_buffer.canvas()->drawImage(image.get(), 0, 0);
+  SkPaint paint;
+  // Copy the source buffer. Do not perform any blending.
+  paint.setXfermodeMode(SkXfermode::kSrc_Mode);
+  modeset_buffer.canvas()->drawImage(image.get(), 0, 0, &paint);
 }
 
 }  // namespace
 
 ScreenManager::ScreenManager(ScanoutBufferGenerator* buffer_generator)
     : buffer_generator_(buffer_generator) {
 }
 
 ScreenManager::~ScreenManager() {
 }
@@ skipping 196 matching lines @@
 
   // When things go wrong revert back to the previous configuration since
   // it is expected that the configuration would not have changed if
   // things fail.
   (*original)->AddCrtc((*mirror)->RemoveCrtc(drm, crtc));
   (*original)->Enable();
   return false;
 }
 
 }  // namespace ui