Added PPB_Graphics3D_Dev::Resize to let plugins resize the backing surface.

ppapi/c/dev/ppb_graphics_3d_dev.h

Index: ppapi/c/dev/ppb_graphics_3d_dev.h
===================================================================
--- ppapi/c/dev/ppb_graphics_3d_dev.h	(revision 94518)
+++ ppapi/c/dev/ppb_graphics_3d_dev.h	(working copy)
@@ -196,6 +196,18 @@
   int32_t (*SetAttribs)(PP_Resource context,
                         int32_t* attrib_list);
 
+  // Resizes the backing surface for context.
+  //
+  // On failure the following error codes may be returned:
+  // - PP_ERROR_BADRESOURCE if context is invalid.
+  // - PP_ERROR_BADARGUMENT if the value specified for width or height
+  //   is less than zero.
+  // - PP_ERROR_NOMEMORY if the surface could not be resized due to
+  //   insufficient resources.

[piman, 2011/07/28 23:35:06]

You won't know about this case without doing a sync round-trip to the gpu
process. I think it would be better in general to treat this as a GL command
(after all it's just glResizeCHROMIUM), returning no error here, but setting the
GL error. If the plugin cares, it can call glGetError which will do the round
trip.

[alokp, 2011/07/29 16:13:12]

Yes I was worried about the round-trip, hence the TODO. There are a couple of
options to avoid the round trip:

1. Expose this as a GL function as you suggest. It is certainly practical but
not very clean API. We create and swap buffers in this interface. But having to
jump over to a the GL interface to resize it is confusing. Another problem with
this approach is that we will have to expose this as a GL extension, which by
definition is optional. But this is not optional. It will be impossible to use
Pepper 3D without this extension.

2. Add documentation that while you could issue a resize command here, you need
to call glGetError to catch out-of-memory condition. Again confusing.

3. Make it asynchronous like swap-buffers. One more callback to track may be too
complicated.

4. Make the callback for SwapBuffers accept an error code. This will also get
rid of the PPP_Graphics3D_Dev::Graphics3DContextLost(). After every frame we
could return one of the following errors generated by this interface:
- PP_GRAPHICS3D_ERROR_CONTEXT_LOST
- PP_ERROR_NO_MEMORY

I like the last option the best. It makes the API much simpler.

+  int32_t (*Resize)(PP_Resource context,
+                    int32_t width,
+                    int32_t height);
+
   // Makes the contents of the color buffer available for compositing.
   // This function has no effect on off-screen surfaces - ones not bound
   // to any plugin instance. The contents of ancillary buffers are always