8387291: XSLT transformation fails on accented characters when output is set to HTML instead of XML

[shruacha1234]

When XSLT output method is html, characters supported by the target encoding were serialized as HTML entity references (for example, é as eacute;). This caused failures when the generated output was later processed as XML.

Solution:
Update HTML serializer to write characters directly when they are supported by the configured encoding, and retain existing entity escaping behavior for unsupported characters.

Testing:
Verified XSLT transformation with accented characters and confirmed generated output can be parsed successfully without XML parsing failures.

Performed Tier1 and Tier2 tests in Linux with and without the fix. No regression found

The bug report for the same: https://bugs.openjdk.org/browse/JDK-8387291

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Issue

• JDK-8387291: XSLT transformation fails on accented characters when output is set to HTML instead of XML (Bug - P4)

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