Add synthetic delay points for latency testing

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 724d537d7a7039de659aeba7ab542f7532ed7765..ad6e1ecb997d74ed66f17abe841333415d52c691 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -17,6 +17,7 @@
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
+#include "base/debug/trace_event_synthetic_delay.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
@@ -8944,6 +8945,10 @@ void GLES2DecoderImpl::DoSwapBuffers() {
   TRACE_EVENT2("gpu", "GLES2DecoderImpl::DoSwapBuffers",
                "offscreen", is_offscreen,
                "frame", this_frame_number);
+  {
+    TRACE_EVENT_SYNTHETIC_DELAY("gpu.SwapBuffers");
+  }
+
   bool is_tracing;
   TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT("gpu.debug"),
                                      &is_tracing);