[windows] Convert usages of GetDC to HWndDC Part 2.

[windows] Convert usages of GetDC to HWndDC Part 2.
https://bugs.webkit.org/show_bug.cgi?id=76750

Reviewed by Adam Roben.

Source/WebKit/win:

* FullscreenVideoController.cpp:
(createCompatibleDCForWindow): Moved out the code which creates a DC for a window
to keep the same scope for the DC lifetime.
(FullscreenVideoController::draw):  Switch to using OwnPtr<HDC>
since createCompatibleDCForWindow returns a PassOwnPtr.
* WebNodeHighlight.cpp:
(WebNodeHighlight::update):
  Cleaned up leaks from calling GetDC without release.
  Note that there is a potential leak of hdc that previously existed
  and still does in an early exit scenario. (This could be easily fixed
  by using OwnPtr<HDC> but I was trying to keep this patch focused.)
* WebView.cpp:
(WebView::scrollBackingStore): Typical conversion.
(WebView::updateBackingStore): Reduced the scope of windowDC to be
right where it is being used.
(WebView::performLayeredWindowUpdate): Typical conversion.
(WebView::paintIntoBackingStore): Ditto.

Source/WebKit2:

* Shared/win/ShareableBitmapWin.cpp:
(WebKit::ShareableBitmap::windowsContext): Fix incorrect usage of OwnPtr<HDC> which
would do a DeleteDC instead of a ReleaseDC.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@105667 268f45cc-cd09-0410-ab3c-d52691b4dbfc