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

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
===================================================================
--- chrome/common/pref_names.cc	(revision 186737)
+++ chrome/common/pref_names.cc	(working copy)
@@ -2163,6 +2163,10 @@
 // Set to true if background mode is enabled on this browser.
 const char kBackgroundModeEnabled[] = "background_mode.enabled";
 
+// Set to true if hardware acceleration mode is enabled on this browser.
+const char kHardwareAccelerationModeEnabled[] =
+  "hardware_acceleration_mode.enabled";
+
 // List of protocol handlers.
 const char kRegisteredProtocolHandlers[] =
   "custom_handlers.registered_protocol_handlers";