Add trace events to measure GPU process startup timing and time to first present.

content/gpu/gpu_info_collector_linux.cc

Index: content/gpu/gpu_info_collector_linux.cc
===================================================================
--- content/gpu/gpu_info_collector_linux.cc	(revision 137679)
+++ content/gpu/gpu_info_collector_linux.cc	(working copy)
@@ -8,6 +8,7 @@
 #include <vector>
 
 #include "base/command_line.h"
+#include "base/debug/trace_event.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
@@ -175,6 +176,8 @@
 bool CollectGraphicsInfo(content::GPUInfo* gpu_info) {
   DCHECK(gpu_info);
 
+  TRACE_EVENT0("gpu", "gpu_info_collector::CollectGraphicsInfo");
+
   if (CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kGpuNoContextLost)) {
     gpu_info->can_lose_context = false;