A mostly-automated change to convert instances of WrapUnique(new Foo(...)) to
MakeUnique<Foo>(...). See the thread at
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/iQgMedVA8-k
for background.

To avoid requiring too many manual fixups, the change skips some cases that are
frequently problematic. In particular, in methods named Foo::Method() it will
not try to change WrapUnique(new Foo()) to MakeUnique<Foo>(). This is because
Foo::Method() may be accessing an internal constructor of Foo.

Cases where MakeUnique<NestedClass>(...) is called within a method of
OuterClass are common but hard to detect automatically, so have been fixed-up
manually.

The only types of manual fix ups applied are:
1) Revert MakeUnique back to WrapUnique
2) Change NULL to nullptr in argument list (MakeUnique cannot forward NULL
   correctly)
3) Add base:: namespace qualifier where missing.

WrapUnique(new Foo) has not been converted to MakeUnique<Foo>() as this might
change behaviour if Foo does not have a user-defined constructor. For example,
WrapUnique(new int) creates an unitialised integer, but MakeUnique<int>()
creates an integer initialised to 0.

git cl format has been been run over the CL. Spot-checking has uncovered no
cases of mis-formatting.

  BUG=637812

Review-Url: https://codereview.chromium.org/2253233004
Cr-Commit-Position: refs/heads/master@{#413390}