[llvm-cov] Simplify the way expansion views are rendered (NFC)

If a sub-view has already been rendered, it's helpful to re-render the
expansion site before rendering the next expansion view. Make this fact
explicit in the rendering interface, instead of hiding it behind an
awkward Optional<LineRef> parameter.

llvm-svn: 273789
diff --git a/llvm/tools/llvm-cov/SourceCoverageViewText.h b/llvm/tools/llvm-cov/SourceCoverageViewText.h
index 36b7c96..17f2e79 100644
--- a/llvm/tools/llvm-cov/SourceCoverageViewText.h
+++ b/llvm/tools/llvm-cov/SourceCoverageViewText.h
@@ -31,12 +31,13 @@
                   CoverageSegmentArray Segments, unsigned ExpansionCol,
                   unsigned ViewDepth) override;
 
-  unsigned renderExpansionView(raw_ostream &OS, ExpansionView &ESV,
-                               Optional<LineRef> FirstLine,
-                               const coverage::CoverageSegment *WrappedSegment,
-                               CoverageSegmentArray Segments,
-                               unsigned ExpansionCol,
-                               unsigned ViewDepth) override;
+  void renderExpansionSite(raw_ostream &OS, ExpansionView &ESV, LineRef L,
+                           const coverage::CoverageSegment *WrappedSegment,
+                           CoverageSegmentArray Segments, unsigned ExpansionCol,
+                           unsigned ViewDepth) override;
+
+  void renderExpansionView(raw_ostream &OS, ExpansionView &ESV,
+                           unsigned ViewDepth) override;
 
   void renderInstantiationView(raw_ostream &OS, InstantiationView &ISV,
                                unsigned ViewDepth) override;