Do not discard existing gpu driver workarounds when called from gpu process

gpu/config/gpu_driver_bug_list.cc

 // Copyright (c) 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 "gpu/config/gpu_driver_bug_list.h"
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "gpu/config/gpu_driver_bug_workaround_type.h"
+#include "gpu/config/gpu_switches.h"
+#include "gpu/config/gpu_util.h"
 
 namespace gpu {
 
 namespace {
 
 struct GpuDriverBugWorkaroundInfo {
   GpuDriverBugWorkaroundType type;
   const char* name;
 };
 
@@ skipping 31 matching lines @@
     return kFeatureList[type].name;
   else
     return "unknown";
 }
 
 // static
 void GpuDriverBugList::AppendWorkaroundsFromCommandLine(
     std::set<int>* workarounds,
     const base::CommandLine& command_line) {
   DCHECK(workarounds);
+
+  if (command_line.HasSwitch(switches::kGpuDriverBugWorkarounds)) {
+    std::string cmd_workarounds_str =
+        command_line.GetSwitchValueASCII(switches::kGpuDriverBugWorkarounds);
+    std::set<int> cmd_workarounds;
+    gpu::StringToFeatureSet(cmd_workarounds_str, &cmd_workarounds);
+    workarounds->insert(cmd_workarounds.begin(), cmd_workarounds.end());
+  }
+
   for (int i = 0; i < NUMBER_OF_GPU_DRIVER_BUG_WORKAROUND_TYPES; i++) {
     if (command_line.HasSwitch(kFeatureList[i].name)) {
       // Check for disabling workaround flag.
       if (command_line.GetSwitchValueASCII(kFeatureList[i].name) == "0") {
         workarounds->erase(kFeatureList[i].type);
         continue;
       }
 
       // Removing conflicting workarounds.
       switch (kFeatureList[i].type) {
@@ skipping 16 matching lines @@
         default:
           workarounds->insert(kFeatureList[i].type);
           break;
       }
     }
   }
 }
 
 }  // namespace gpu