With the conversion between StringRef and std::string now being explicit, converting SmallStrings becomes more tedious. This patch adds an explicit operator so you can write std::string(Str) instead of Str.str().str().
Unit tests: fail. 62303 tests passed, 1 failed and 838 were skipped.
I'm late here, but that should probably be this->data() instead of this->begin(). It does the same thing in this case, but begin() returns an "iterator" while data() returns a pointer. And the constructor that's being called is defined as taking a pointer and size.