Add a user pref in Settings to disable all GPU features.

content/browser/gpu/gpu_data_manager_impl.cc

Index: content/browser/gpu/gpu_data_manager_impl.cc
===================================================================
--- content/browser/gpu/gpu_data_manager_impl.cc	(revision 186737)
+++ content/browser/gpu/gpu_data_manager_impl.cc	(working copy)
@@ -496,7 +496,7 @@
   return gpu_switching_;
 }
 
-void GpuDataManagerImpl::BlacklistCard() {
+void GpuDataManagerImpl::DisableHardwareAcceleration() {
   card_blacklisted_ = true;
 
   blacklisted_features_ = GPU_FEATURE_TYPE_ALL;
@@ -608,7 +608,7 @@
     command_line->AppendSwitch(switches::kDisableAcceleratedLayers);
   }
   if (command_line->HasSwitch(switches::kDisableGpu))
-    BlacklistCard();
+    DisableHardwareAcceleration();
   if (command_line->HasSwitch(switches::kGpuSwitching)) {
     std::string option_string = command_line->GetSwitchValueASCII(
         switches::kGpuSwitching);