ScopedVector - fix const semantics.

ScopedVector - fix const semantics.

const std::vector<T*> returns a const reference to a T* for
operator[]. const ScopedVector<T> instead returns a const T*, which
means the two have slightly differing semantics.

Fix ScopedVector to behave like std::vector instead - the reference
to the pointer is const, but the pointer is not const.

TBR=willchan@chromium.org
R=brettw@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=209537

[groby-ooo-7-16, 2013-06-27 19:55:53]

will: I suppose this was an oversight - it prevents using ScopedVector in some
cases where we currently use std::vector<>/STLDeleteContainerPointer. (Mostly
accessors on a class that return a T*, but are declared const themselves). 

If this is a design decision for ScopedVector instead, consider this moot.


As for the change, I suppose I could've used void* const& instead of
const_reference, but I like having the API similar to std::vector.

(For the same reason, changed T*& to reference)

[groby-ooo-7-16, 2013-06-29 01:47:18]

Changed reviewers, since willchan seems to be occupied otherwise right now.

brettw: PTAL

[brettw, 2013-07-01 05:01:06]

lgtm

[commit-bot: I haz the power, 2013-07-01 17:28:05]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/groby@chromium.org/18131002/1

[commit-bot: I haz the power, 2013-07-01 23:26:15]

Change committed as 209537