History has a lot of vectors of structs that include things like URLs and strings that could benefit from move constructors. This implements move constructors on such classes in history_types.h.

Moves initialization of many values from explicit constructor initializer lists to the class definition for clarity and de-duplication. For URLRow this allowed removing the Initialize() helper function.

Some structs were using implicitly defined copy and assignment operators. These are defined now so they can be out-of-line for code bloat reasons.

An unused constructor on URLResult is removed.

Out-of-date references to dirty bits in comments in URLRow are removed. These dirty bits no longer exist.

Friend declarations in URLRow (these were related to handling of the aforementioned dirty bits) were removed and two places depending on these friend declarations were changed to use set_*() functions instead. A set_url() function was added which was the only missing setter.

Review-Url: https://codereview.chromium.org/2781263002
Cr-Commit-Position: refs/heads/master@{#461159}