Fix background corruption in scrolled wxHtmlWindow.

Draw the background on the entire virtual size, not just the currently shown
client size.

Closes #15047.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73543 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
No real changes, just suppress a harmless warning.

g++ warned about possibly uninitialized variable, so initialize it in its
declaration even if it was actually already always initialized in the branches
where it could be used.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73548 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775
Fix crash when drawing bitmaps with mask in wxGTK with GTK+ < 2.20.

r73386 introduced a crash in wxGTK drawing code when using old GTK+ versions
by releasing the mask pixmap prematurely. Apparently GTK+ itself was fixed at
some time in 2.19.x time frame but work around the bug for the sake of older
GTK+ versions in wxGTK itself by simply releasing the pixmap at the end of
DoDrawBitmap(), as pre-r73386 code did.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@73549 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775