New thunk system for Pepper proxy and implementation

This implements the new system for Graphics2D only.

This works by adding a new thunk layer that will forward to an "API" that's either per-instance (function APIs) or per-resource (resource APIs). The proxying and such is then implemented in terms of this C++ API.

Ideally the trackers of the PP_Resource/PP_Instance -> object mapping would be shared between the plugin and renderer processes. To keep this patch under control, I did this as a virtual base class which is implemented by ppapi::proxy::PluginResourceTracker and webkit::ppapi::ResourceTracker. Later, the functionality of these objects should be shared in a common tracker class.

Still to do it a lot of cleanup and merging of things. Also, the namespaces are a bit out of control.
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=84519

[brettw, 2011-05-06 16:42:47]

I think this is a reasonable stopping point for the first patch. There is still
a lot of stuff to do. In particular, the namespaces are kind of a mess, as is
the way that the resource objects are instantiated (because we need to keep
supporting the old way).

Changed since we discussed this: I made the function API ID deduced by the
templates. I added an ImageData proxy, which turned out fairly nicely. I made
the Graphics2D proxy not call through to the C interface and instead use the
"Enter" object to skip to C++.

[piman, 2011-05-06 17:00:09]

LGTM, some nits

http://codereview.chromium.org/6905088/diff/24001/ppapi/shared_impl/tracker_b...
File ppapi/shared_impl/tracker_base.cc (right):

http://codereview.chromium.org/6905088/diff/24001/ppapi/shared_impl/tracker_b...
ppapi/shared_impl/tracker_base.cc:12: static TrackerBase* (*global_getter)() =
NULL;
g_global_getter

http://codereview.chromium.org/6905088/diff/24001/ppapi/thunk/enter.h
File ppapi/thunk/enter.h (right):

http://codereview.chromium.org/6905088/diff/24001/ppapi/thunk/enter.h#newcode45
ppapi/thunk/enter.h:45: // this internally).
Remove TODO since it's done

http://codereview.chromium.org/6905088/diff/24001/ppapi/thunk/enter.h#newcode46
ppapi/thunk/enter.h:46: EnterFunction(PP_Instance instance, bool report_error)
You could make report_error a template parameter. Up to you.

http://codereview.chromium.org/6905088/diff/24001/webkit/plugins/ppapi/ppb_gr...
File webkit/plugins/ppapi/ppb_graphics_2d_impl.h (right):

http://codereview.chromium.org/6905088/diff/24001/webkit/plugins/ppapi/ppb_gr...
webkit/plugins/ppapi/ppb_graphics_2d_impl.h:51: PP_Bool Describe(PP_Size* size,
PP_Bool* is_always_opaque);
virtual on this and the next ones