LOK unit tests: document what is a view callback

Change-Id: Ic605ca12cebfb6fd8239829942bbc6a70f45ac06
Reviewed-on: https://gerrit.libreoffice.org/28168Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>

sc/qa/unit/tiledrendering/tiledrendering.cxx

@@ -370,6 +370,7 @@ void ScTiledRenderingTest::testEmptyColumnSelection()
     comphelper::LibreOfficeKit::setActive(false);
 }
 
+/// A view callback tracks callbacks invoked on one specific view.
 class ViewCallback
 {
 public:

sd/qa/unit/tiledrendering/tiledrendering.cxx

@@ -855,6 +855,7 @@ void SdTiledRenderingTest::testResizeTableColumn()
     comphelper::LibreOfficeKit::setActive(false);
 }
 
+/// A view callback tracks callbacks invoked on one specific view.
 class ViewCallback
 {
 public:

sw/qa/extras/tiledrendering/tiledrendering.cxx

@@ -571,6 +571,7 @@ void SwTiledRenderingTest::testPartHash()
     comphelper::LibreOfficeKit::setActive(false);
 }
 
+/// A view callback tracks callbacks invoked on one specific view.
 class ViewCallback
 {
 public: