Add new ref-counted Renderbuffer class.

Renderbuffers are a clear object type in GL, and this patch adds
a more consistent state representation for them. They're managed
by the ResourceManager, and have a storage implementation similar
to Textures, but much simpler.

BUG=angle:660

Change-Id: Ia17199bb8cb570d48db42e1f28ccbcc12a902fcf
Reviewed-on: https://chromium-review.googlesource.com/201834
Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shannon Woods <shannonwoods@chromium.org>
diff --git a/src/libGLESv2/Framebuffer.h b/src/libGLESv2/Framebuffer.h
index 1a5e2b6..0c5a8d7 100644
--- a/src/libGLESv2/Framebuffer.h
+++ b/src/libGLESv2/Framebuffer.h
@@ -22,6 +22,7 @@
 namespace gl
 {
 class FramebufferAttachment;
+class FramebufferAttachmentImpl;
 class Colorbuffer;
 class Depthbuffer;
 class Stencilbuffer;
@@ -99,7 +100,7 @@
   private:
     DISALLOW_COPY_AND_ASSIGN(Framebuffer);
 
-    FramebufferAttachment *lookupAttachment(GLenum type, GLuint handle, GLint level, GLint layer) const;
+    FramebufferAttachmentImpl *createAttachmentImpl(GLenum type, GLuint handle, GLint level, GLint layer) const;
 };
 
 class DefaultFramebuffer : public Framebuffer