GitLab

Replaced several of scoped_refptr's assignment operators by a unified assignment
operator. This works beautifully in tandem with scoped_refptr's different
constructors, and it removes some duplicated and tricky code. It is exception
safe, and works fine in case of self assignment.

We still need to keep operator=(T*), despite the implicit conversion constructor
scoped_refptr(T*). There is code assigning rtc::scoped_refptr<T> to
scoped_refptr<T>, and we want to keep this code compiling and working as is.
rtc::scoped_refptr<T> has an implicit conversion operator to T*. C++ allows one
implicit conversion, but not two, to be chained in a row.

Marked scoped_refptr's move and swap operations as noexcept. This allows
std::vector<scoped_refptr<T>> to use scoped_refptr's more efficient move
operations instead of copy operations. This avoids extraneous calls to
T::AddRef() and T::Release() when vector is reallocating its internal buffer.

Change-Id: Id6f360f8acab827133fe5bef829a7a2e308b87fd
Reviewed-on: https://chromium-review.googlesource.com/802338Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: François Degros <fdegros@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524008}