Add more strict DCHECKs around context state.

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 5b59fdbbc29cc20d9f8679e9b222430f23afab6d..1319780ccd003301daa1c79b82f14c513b175379 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -5239,6 +5239,7 @@ error::Error GLES2DecoderImpl::DoCommandsImpl(unsigned int num_commands,
                                               const volatile void* buffer,
                                               int num_entries,
                                               int* entries_processed) {
+  DCHECK(context_->IsCurrent(surface_.get()));
   commands_to_process_ = num_commands;
   error::Error result = error::kNoError;
   const volatile CommandBufferEntry* cmd_data =