Allow GL_TEXTURE_RECTANGLE_ARB to be the destination target for copyTextureCHROMIUM.

gpu/command_buffer/service/texture_manager.cc

Index: gpu/command_buffer/service/texture_manager.cc
diff --git a/gpu/command_buffer/service/texture_manager.cc b/gpu/command_buffer/service/texture_manager.cc
index 1bce4948bab4498d66e1d86e61a57243830a66c7..8b1bbd0bb633a5c83bf2454e9caffad287e496c3 100644
--- a/gpu/command_buffer/service/texture_manager.cc
+++ b/gpu/command_buffer/service/texture_manager.cc
@@ -1929,14 +1929,7 @@ bool TextureManager::ValidateTexImage(
         error_state, function_name, args.target, "target");
     return false;
   }
-  // TODO(ccameron): Add a separate texture from |texture_target| for
-  // [Compressed]Tex[Sub]Image2D and related functions.
-  // http://crbug.com/536854
-  if (args.target == GL_TEXTURE_RECTANGLE_ARB) {
-    ERRORSTATE_SET_GL_ERROR_INVALID_ENUM(
-        error_state, function_name, args.target, "target");
-    return false;
-  }

[piman, 2016/01/05 01:36:39]

Your change seems unrelated to glTexImage2D and friends, where we still need to
disable GL_TEXTURE_RECTANGLE_ARB as a target (IIUC because uploading software
pixels to an HW-backed IOSurface causes trouble), so I think you need to keep
this here.

[erikchen, 2016/01/05 01:45:15]

I commented on this in patch set 10:
https://codereview.chromium.org/1547873002/diff/100002/gpu/command_buffer/ser...

Could you please clarify what code will call glTexImage2D() with
GL_TEXTURE_RECTANGLE_ARB as a target on an IOSurface backed texture? 

I removed this check because the unit test I added needed to call glTexImage2D()
with target=GL_TEXTURE_RECTANGLE_ARB on a non-IOSurface backed texture. If we
need to keep this check, can you suggest how should I restructure the unit test?

[piman, 2016/01/05 02:13:23]

Actually, my recollection was slightly incorrect, the bad case is binding an
IOSurface after using glTexImage2D. I think Flash would do that - see
https://code.google.com/p/chromium/issues/detail?id=518744 - though it may have
been updated since then. The decision was to disallow uploading texels
altogether on a GL_TEXTURE_RECTANGLE_ARB texture, hence this code.
But either way, the client is untrusted, we can't assume it will only do the
right thing.

 
My suggestion would be to model the test after the use case we have for
GL_TEXTURE_RECTANGLE_ARB, namely binding an IOSurface, instead of uploading
texels.

[erikchen, 2016/01/05 23:54:03]

I updated the test and added this logic back to texture_manager.cc.

+
   if (!ValidateTextureParameters(
       error_state, function_name, args.format, args.type,
       args.internal_format, args.level)) {