cc: Make single-thread renderer compositor always synchronous.

content/browser/gpu/compositor_util.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/browser/gpu/compositor_util.h"
 
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 239 matching lines @@
 
 #if defined(OS_ANDROID)
   return false;
 #endif
   return true;
 }
 
 bool IsZeroCopyUploadEnabled() {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
+  // Single-threaded mode in the renderer process (for layout tests) is
+  // synchronous, which depends on tiles being ready to draw when raster is
+  // complete.  Therefore, it must use one of zero copy, software raster, or
+  // GPU raster. So we force zero-copy on for the case where software/GPU raster
+  // is not used.
+  // TODO(reveman): One-copy can work with sync compositing: crbug.com/490295.
+  if (command_line.HasSwitch(switches::kDisableThreadedCompositing))
+    return true;
   return command_line.HasSwitch(switches::kEnableZeroCopy);
 }
 
 bool IsGpuRasterizationEnabled() {
   const base::CommandLine& command_line =
       *base::CommandLine::ForCurrentProcess();
 
   if (!IsImplSidePaintingEnabled())
     return false;
 
@@ skipping 164 matching lines @@
     }
   }
   return problem_list;
 }
 
 std::vector<std::string> GetDriverBugWorkarounds() {
   return GpuDataManagerImpl::GetInstance()->GetDriverBugWorkarounds();
 }
 
 }  // namespace content