Turned on PbufferImageTransportSurface as default image transport for vista and win 7 (not XP).

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
===================================================================
--- content/public/common/content_switches.cc	(revision 113603)
+++ content/public/common/content_switches.cc	(working copy)
@@ -107,6 +107,10 @@
 // Manager can be used to terminate the offending process in this case.
 const char kDisableHangMonitor[]            = "disable-hang-monitor";
 
+// Disable the use of an ImageTransportSurface. This means the GPU process
+// will present the rendered page rather than the browser process.
+const char kDisableImageTransportSurface[]  = "disable-image-transport-surface";
+
 // Disable the thread that crashes the GPU process if it stops responding to
 // messages.
 const char kDisableGpuWatchdog[]            = "disable-gpu-watchdog";