Implement debug marker entry points in the passthrough command buffer.

gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc b/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc
index ae441dbd0d3f2300531479625c60bd83567f1b9d..c32308a1b83b8ca1abf8d239b272e27e5fdf5e1d 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder_passthrough_doers.cc
@@ -2498,19 +2498,31 @@ error::Error GLES2DecoderPassthroughImpl::DoSetDisjointValueSyncCHROMIUM(
 error::Error GLES2DecoderPassthroughImpl::DoInsertEventMarkerEXT(
     GLsizei length,
     const char* marker) {
-  NOTIMPLEMENTED();
+  if (!feature_info_->feature_flags().ext_debug_marker) {
+    return error::kUnknownCommand;
+  }
+
+  glInsertEventMarkerEXT(length, marker);
   return error::kNoError;
 }
 
 error::Error GLES2DecoderPassthroughImpl::DoPushGroupMarkerEXT(
     GLsizei length,
     const char* marker) {
-  NOTIMPLEMENTED();
+  if (!feature_info_->feature_flags().ext_debug_marker) {
+    return error::kUnknownCommand;
+  }
+
+  glPushGroupMarkerEXT(length, marker);
   return error::kNoError;
 }
 
 error::Error GLES2DecoderPassthroughImpl::DoPopGroupMarkerEXT() {
-  NOTIMPLEMENTED();
+  if (!feature_info_->feature_flags().ext_debug_marker) {
+    return error::kUnknownCommand;
+  }
+
+  glPopGroupMarkerEXT();
   return error::kNoError;
 }