Windows: Improvements to off-screen rendering support (issue #518).

- Implement support for transparency. Change the backing store to use Skia instead of GDI and to keep alpha values.
- Implement support for select popups. Requires a patch to Chromium (content_popups.patch).
- Implicitly disable accelerated compositing when using off-screen rendering.
- Introduce a new CefMouseEvent structure for representing mouse event information passed to CefBrowser methods.
- Merge cef_key_event_modifiers_t into cef_event_flags_t.
- Add a new argument to CefBrowser::Invalidate telling the browser whether to invalidate the select popup or the main view.
- Add a new cefclient "transparent-painting-enabled" command-line flag to test transparent off-screen rendering.
- Add a new cefclient "Transparency" test.
- Fix the cefclient off-screen rendering rotation effect to work even when the underlying web content is not updating.
- Add unit tests for transparent painting and select popups.

git-svn-id: https://chromiumembedded.googlecode.com/svn/trunk@979 5089003a-bbd8-11dd-ad1f-f1f9622dbc98

tests/cefclient/osrenderer.h

@@ -43,6 +43,11 @@ class ClientOSRenderer {
   int GetViewWidth() { return view_width_; }
   int GetViewHeight() { return view_height_; }
 
+  const CefRect& popup_rect() const { return popup_rect_; }
+  const CefRect& original_popup_rect() const { return original_popup_rect_; }
+
+  CefRect GetPopupRectInWebView(const CefRect& original_rect);
+
  private:
   bool transparent_;
   bool initialized_;
@@ -50,6 +55,7 @@ class ClientOSRenderer {
   int view_width_;
   int view_height_;
   CefRect popup_rect_;
+  CefRect original_popup_rect_;
   float spin_x_;
   float spin_y_;
 };