[EFL][WK2] Rely more on C API in ewk_favicon_database
https://bugs.webkit.org/show_bug.cgi?id=108035

Reviewed by Benjamin Poulain.

Rely less on internal C++ API in ewk_favicon_database and use C API
instead of avoid breaking API layering.

* PlatformEfl.cmake:
* UIProcess/API/C/cairo/WKIconDatabaseCairo.cpp: Added.
(WKIconDatabaseTryGetCairoSurfaceForURL): Add C API for getting the
favicon for a given page URL as a cairo_surface_t*.
* UIProcess/API/C/cairo/WKIconDatabaseCairo.h: Added.
* UIProcess/API/efl/ewk_favicon_database.cpp:
(EwkFaviconDatabase::didChangeIconForPageURL):
(EwkFaviconDatabase::getIconSurfaceSynchronously):
(EwkFaviconDatabase::iconDataReadyForPageURL):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@140952 268f45cc-cd09-0410-ab3c-d52691b4dbfc