Load the GL_KHR_debug entry points and log messages they produce.

gpu/command_buffer/service/gles2_cmd_decoder_passthrough.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder_passthrough.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_passthrough.cc b/gpu/command_buffer/service/gles2_cmd_decoder_passthrough.cc
index 17c723f0c7858a7b6d5b0851e617d43c5c22ff6f..6636439457a6512683be6e53f0f6e97d3e926041 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_passthrough.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_passthrough.cc
@@ -178,6 +178,11 @@ bool GLES2DecoderPassthroughImpl::Initialize(
   active_texture_unit_ = 0;
   bound_textures_.resize(num_texture_units, 0);
 
+  if (group_->gpu_preferences().enable_gpu_driver_debug_logging &&
+      feature_info_->feature_flags().khr_debug) {
+    InitializeGLDebugLogging();
+  }
+
   set_initialized();
   return true;
 }