[jdk8u-dev] RFR: 8212678: Windows IME related patch

[Takuya Kiriyama]

Hi All,  

I would like to backport this bug fix (JDK-8212768) done in jdk13 to jdk8. It is basically a clean backport, but only the copyright of awt_InputMethod.cpp and awt_Component.cpp is not updated because the current source is newer.  

The following fixes are resolved.

**Issue A: Cannot display surrogate pair character on Windows floating IME window for passive component**  
It has been reproduced using the test program (SwingSet2) in a specific environment and verified that this fix resolves it. 

**Issue B: Control Windows IME status using InputSubset and UnicodeBlock for CJK countries**  
It has been reproduced using the test program (ImSubsetsTest.java) in a specific environment and verified that this fix resolves it. 

**Issue C: Check pre-edit string availability for Windows Chinese IME**  
It probably won't happen again in the new environment. I have verified that the behavior of the test program  (IMFTestA.java) remains unchanged after this fix.

JTREG tests were executed using the `-a` option (automatic tests only) for the test suites  java/awt/Component and java/awt/InputMethods. No failures were found.

The changes implemented in JDK-8212678 alone are not sufficient to fully resolve IME-related issues. To ensure a complete fix, the changes from JDK-8258805 must also be integrated.
I plan to create a separate pull request.

Thank you.

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Commit messages:
 - 8212678: Windows IME related patch

Changes: https://git.openjdk.org/jdk8u-dev/pull/706/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=706&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8212678
  Stats: 40 lines in 3 files changed: 38 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/706.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/706/head:pull/706

PR: https://git.openjdk.org/jdk8u-dev/pull/706