The destructor did not release D3D objects that could be in the
mPendingQueries list when the destructor is called. This fix now iterates
through the list and releases them.

BUG=angleproject:1325

Change-Id: Ia3bd2a8a611f8dbf85051ab5bfea18ab72038af5
Reviewed-on: https://chromium-review.googlesource.com/329426Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Ian Ewell <ewell@google.com>