Automated sync from github.com/tensorflow/tensorflow (#2662)

BUG=automated sync from upstream
NO_CHECK_TFLITE_FILES=automated sync from upstream
diff --git a/tensorflow/lite/core/c/common.h b/tensorflow/lite/core/c/common.h
index 96f19f1..648b862 100644
--- a/tensorflow/lite/core/c/common.h
+++ b/tensorflow/lite/core/c/common.h
@@ -100,7 +100,9 @@
   TfLiteStatus (*Refresh)(struct TfLiteContext* context);
 } TfLiteExternalContext;
 
+// LINT.IfChange(optional_tensor)
 #define kTfLiteOptionalTensor (-1)
+// LINT.ThenChange(//tensorflow/compiler/mlir/lite/flatbuffer_export.cc:optional_tensor)
 
 /// Fixed size list of integers. Used for dimensions and inputs/outputs tensor
 /// indices