command_buffer: Avoid glGetError after lost context

Do not call glGetError for debug info after context has been lost.

BUG=581634
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_optional_gpu_tests_rel;tryserver.chromium.mac:mac_optional_gpu_tests_rel;tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/1922703004
Cr-Commit-Position: refs/heads/master@{#390332}

gpu/command_buffer/service/gles2_cmd_decoder.cc

@@ -4473,7 +4473,7 @@ error::Error GLES2DecoderImpl::DoCommandsImpl(unsigned int num_commands,
         if (DebugImpl && doing_gpu_trace)
           gpu_tracer_->End(kTraceDecoder);
 
-        if (DebugImpl && debug()) {
+        if (DebugImpl && debug() && !WasContextLost()) {
           GLenum error;
           while ((error = glGetError()) != GL_NO_ERROR) {
             LOG(ERROR) << "[" << logger_.GetLogPrefix() << "] "