See bug #337386 for some context.

In the testcase that was causing this problem, we do the following:
  1) Create pipeline.
  2) Create bin.
  3) Create fakesink
  4) Put fakesink in bin
  5) Put bin in pipeline

At step 5, we get a bogus clock-provide message being created (bogus because fakesink is NOT a clock provider).

The reason for this is that, when we add something to a bin (in this case adding a bin to a pipeline), we create the clock-provide message if  gst_element_provides_clock() returns TRUE for the element being added.

For fakesink, this correctly returns false (so when we add the fakesink to the bin, we don't create a message).

However, for the bin, it returns true: we return true in gst_element_provides_clock() if the element has a provide_clock vfunc. For a bin, we always have this vfunc, regardless of whether any of our children provide clocks. This is wrong.