sw: paragraph-sign: avoid re-validating paragraphs when classifying

When setting the classification watermark, every edit to the document
is triggering a re-validation of signatures, which is excessive and
excessively expensive.

Change-Id: I7808877263f553a871f2c31856da1a2f9e50c4bb
Reviewed-on: https://gerrit.libreoffice.org/63007
Tested-by: Jenkins
Reviewed-by: Ashod Nakashian <ashnakash@gmail.com>

sw/source/core/edit/edfcol.cxx

@@ -2160,6 +2160,12 @@ void SwEditShell::ClassifyDocPerHighestParagraphClass()
 
     const SfxClassificationPolicyType eHighestClassType = SfxClassificationHelper::stringToPolicyType(sHighestClass);
 
+    // Prevent paragraph signature validation since the below changes (f.e. watermarking) are benign.
+    const bool bOldValidationFlag = SetParagraphSignatureValidation(false);
+    comphelper::ScopeGuard const g([this, bOldValidationFlag]() {
+        SetParagraphSignatureValidation(bOldValidationFlag);
+    });
+
     // Check the origin, if "manual" (created via advanced classification dialog),
     // then we just need to set the category name.
     if (sfx::getCreationOriginProperty(xPropertyContainer, aKeyCreator) == sfx::ClassificationCreationOrigin::MANUAL)