[clang] [clang][Diagnostics] Only record lexer check points when colors are enabled (PR #204926)

[Yihan Wang via cfe-commits]

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@@ -383,6 +383,9 @@ class Preprocessor {
   llvm::DenseMap<FileID, SmallVector<const char *>> CheckPoints;
   unsigned CheckPointCounter = 0;
 
+  /// Whether to record lexer check points for diagnostic snippet highlighting.
+  bool RecordCheckPoints = false;
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yronglin wrote:

IIUC, this change shouldn't have a significant performance impact; it simply reduces the number of flags in the Preprocessor. Since it's exactly the same as ShowColors, I tend to use ShowColors directly. If whether to record check points is determined by multiple conditions, then I'd prefer to add a new flag. 

https://github.com/llvm/llvm-project/pull/204926