Cannot save file in UTF-8 correctly

[snjeza]

Fixes redhat-developer/vscode-java#394

The issue can be reproduced on Windows.

Signed-off-by: Snjezana Peco [email protected]

[gorkem]

@snjeza Can you add an explanation why we are making the change, possibly to commit message or as a comment. It is hard to see how this change fixes this issue.

[snjeza]

The issue has been introduced by fixing redhat-developer/vscode-java#380
We should synchronize a compilation unit with its file system resource when calling the document/didSave command.
unit.commitWorkingCopy() synchronizes them, but, also, saves the buffer to the file system resource. The buffer is saved using the default OS encoding (cp1250 on Windows) and breaks utf8 characters on Windows.
We don't have to the save buffer to the file (the VS Code client does it), but only synchronize it. The PR does it with the following:

unit.discardWorkingCopy();
unit.becomeWorkingCopy(new NullProgressMonitor());

See also #375