gpu: Disallow zero sized offscreen framebuffers

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 04a9eb25443cb2a25d52400ba714c850ea63eca6..86a6c672be4160b64833d9fe9597fa11c91b1633 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -2464,6 +2464,7 @@ bool GLES2DecoderImpl::Initialize(
   TRACE_EVENT0("gpu", "GLES2DecoderImpl::Initialize");
   DCHECK(context->IsCurrent(surface.get()));
   DCHECK(!context_.get());
+  DCHECK(!offscreen || !offscreen_size.IsEmpty());

[hendrikw, 2015/04/24 18:33:39]

In my first change, I also DCHECK'd that glGetError() == GL_NO_ERROR near the
end of the function, but we have some mocks that didn't agree with that.

I think it makes sense to catch this, but maybe I should be calling
LOCAL_COPY_REAL_GL_ERRORS_TO_WRAPPER, then DCHECK on the result of
LOCAL_PEEK_GL_ERROR? 

I suspect that LOCAL_COPY_REAL_GL_ERRORS_TO_WRAPPER will cause the same mock
functions to still fail, but that could probably be fixed, I think I need to
override GetError somewhere.

If an error were to happen, we probably want it copied into the state, right? 
Maybe we want to even fail the initialize when an error occurs (we'd probably
want to check the error going into the function too then).

What do you think?

 
   ContextCreationAttribHelper attrib_parser;
   if (!attrib_parser.Parse(attribs))