[llvm-cov] Remove a redundant field. NFC.

The "NotCovered" fields in the region and line summary structs are
redundant. We should remove them to make the code clearer.

As a follow-up, the "NotCovered" entries should be removed from the
reports as well.

llvm-svn: 313415
diff --git a/llvm/tools/llvm-cov/CoverageExporterJson.cpp b/llvm/tools/llvm-cov/CoverageExporterJson.cpp
index f891326..6ec6974f 100644
--- a/llvm/tools/llvm-cov/CoverageExporterJson.cpp
+++ b/llvm/tools/llvm-cov/CoverageExporterJson.cpp
@@ -395,7 +395,9 @@
     emitDictStart();
     emitDictElement("count", Summary.RegionCoverage.NumRegions);
     emitDictElement("covered", Summary.RegionCoverage.Covered);
-    emitDictElement("notcovered", Summary.RegionCoverage.NotCovered);
+    emitDictElement("notcovered",
+                    Summary.RegionCoverage.NumRegions -
+                        Summary.RegionCoverage.Covered);
     emitDictElement("percent", Summary.RegionCoverage.getPercentCovered());
     // End Region Coverage Summary.
     emitDictEnd();