gpu: Record GL state to trace

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 be644ce11ef3c4088bf6f42fa6eb03582a9d01c1..7007c744a21abc7b2b8f7016def4b5df6c181273 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -42,6 +42,7 @@
 #include "gpu/command_buffer/service/gl_utils.h"
 #include "gpu/command_buffer/service/gles2_cmd_copy_texture_chromium.h"
 #include "gpu/command_buffer/service/gles2_cmd_validation.h"
+#include "gpu/command_buffer/service/gpu_state_tracer.h"
 #include "gpu/command_buffer/service/gpu_switches.h"
 #include "gpu/command_buffer/service/gpu_tracer.h"
 #include "gpu/command_buffer/service/image_manager.h"
@@ -1665,6 +1666,7 @@ class GLES2DecoderImpl : public GLES2Decoder {
   DecoderFramebufferState framebuffer_state_;
 
   scoped_ptr<GPUTracer> gpu_tracer_;
+  scoped_ptr<GPUStateTracer> gpu_state_tracer_;
 
   std::queue<linked_ptr<FenceCallback> > pending_readpixel_fences_;
 
@@ -2129,6 +2131,7 @@ bool GLES2DecoderImpl::Initialize(
 
   set_initialized();
   gpu_tracer_ = GPUTracer::Create();
+  gpu_state_tracer_ = GPUStateTracer::Create(&state_);
 
   if (CommandLine::ForCurrentProcess()->HasSwitch(
       switches::kEnableGPUDebugging)) {
@@ -8575,6 +8578,12 @@ void GLES2DecoderImpl::DoSwapBuffers() {
   TRACE_EVENT2("gpu", "GLES2DecoderImpl::DoSwapBuffers",
                "offscreen", is_offscreen,
                "frame", this_frame_number);
+  bool is_tracing;
+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(TRACE_DISABLED_BY_DEFAULT("gpu.debug"),
+                                     &is_tracing);
+  if (is_tracing)
+    gpu_state_tracer_->TakeSnapshot();

[piman, 2013/09/09 21:25:54]

A non-default framebuffer could be bound when SwapBuffers is called, meaning
glReadPixels in TakeSnapshot will not grab what you expect.

[piman, 2013/09/09 21:25:54]

Could we also do this in HandlePostSubBufferCHROMIUM?

Also, another suggestion is to add a command that would grab the snapshot of the
currently bound framebuffer. In the composite-to-mailbox case, we won't call
SwapBuffers/PostSubBuffers, but it might still be useful to grab the renderer
frame. WDYT?

+
   // If offscreen then don't actually SwapBuffers to the display. Just copy
   // the rendered frame to another frame buffer.
   if (is_offscreen) {