Defeat Clang's enhanced -Wself-assign warning

In 329493, Clang's -Wself-assign warning started also firing on
overloaded assignment operators. The suggested way to suppress it is to
use *& on the right-hand side.

This fixes the instances that fire during a debug build on Linux.

TBR=jochen

Bug: 830338
Change-Id: I5198ff8171462b78d55b84f58358588caf3f7fa2
Reviewed-on: https://chromium-review.googlesource.com/1000856
Commit-Queue: Hans Wennborg <[email protected]>
Reviewed-by: Nico Weber <[email protected]>
Cr-Commit-Position: refs/heads/master@{#549152}
8 files changed