Epiphany extensions, WebKit porting

[Alp Toker <alp atoker com>]

Hi gang,

In the run up to 2.24 I took a first stab at porting some of the 
remaining epiphany-extensions to work with our new WebKit browser engine.

GreaseMonkey is now in the default set of extensions and works for basic 
scripts. We aren't yet installing the callbacks to support the full GM 
API (I'm guessing the old implementation relied partly on the official 
GreaseMonkey extension). There are many examples of how to implement JS 
callbacks -- the nicest is the code in Midori, which provides utilities 
to bridge GObject with JavaScript. It might be worth picking this up or 
borrowing ideas from it -- at the very minimum the string conversion 
utility function. The callbacks that need to be implemented for GM are 
fairly straightforward -- for example there's a preferences API (get/set 
preference) which we can maybe hook up to GConf.

The auto-scroll extension now works. To get this going, I had to replace 
the DOM mouse event callback handlers with a standard GTK+ mouse down 
one. When we get GObject DOM support in WebKit, we'll be able to test 
the element the middle-click is made on to make sure we're not stealing 
clicks from web content, but for now it works well enough without that. 
Porting push-scroll and gestures should be a similar task -- you can 
basically copy what I do in auto-scroll.

If you're already an Epiphany or WebKit/GTK+ contributor, please feel 
free to commit porting changes without review in both epiphany and 
epiphany-extensions. We can back out any changes that cause trouble but 
right now we need to get moving to make sure there are no regressions by 
2.24.

Epiphany core hackers: I need some help factoring out EphyEmbed and 
using WebKit API more directly in the core. To enable this, we need to 
standardise some convenience API to cast from EphyEmbed to WebView for 
incremental porting as Xan suggests. Of course, if anyone wants to take 
a stab at killing off EphyEmbed in one go, that's also good.

Porting is fun! Go go go!