Work around unknown Mac Intel driver bug causing non-deterministic behavior in GPU readback from 2D

content/renderer/render_view_impl.cc

 // Copyright (c) 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 "content/renderer/render_view_impl.h"
 
 #include <algorithm>
 #include <cmath>
 #include <memory>
 
@@ skipping 873 matching lines @@
   // Disable antialiasing of clips for 2d canvas if requested on the command
   // line.
   settings->setAntialiasedClips2dCanvasEnabled(
       prefs.antialiased_clips_2d_canvas_enabled);
 
   // Set MSAA sample count for 2d canvas if requested on the command line (or
   // default value if not).
   settings->setAccelerated2dCanvasMSAASampleCount(
       prefs.accelerated_2d_canvas_msaa_sample_count);
 
+  // Force readback from 2D canvas to use software code path. crbug.com/665656
+  settings->setForceSoftwareReadbackFrom2DCanvas(
+      prefs.force_software_readback_from_2d_canvas);
+
   // Tabs to link is not part of the settings. WebCore calls
   // ChromeClient::tabsToLinks which is part of the glue code.
   web_view->setTabsToLinks(prefs.tabs_to_links);
 
   settings->setAllowRunningOfInsecureContent(
       prefs.allow_running_insecure_content);
   settings->setDisableReadingFromCanvas(prefs.disable_reading_from_canvas);
   settings->setStrictMixedContentChecking(prefs.strict_mixed_content_checking);
 
   settings->setStrictlyBlockBlockableMixedContent(
@@ skipping 1873 matching lines @@
                             INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
   }
 
   std::unique_ptr<InputEventAck> ack(
       new InputEventAck(InputEventAckSource::MAIN_THREAD, input_event->type,
                         INPUT_EVENT_ACK_STATE_NOT_CONSUMED));
   OnInputEventAck(std::move(ack));
 }
 
 }  // namespace content