Allow efficient WebURL -> GURL conversions

Allow efficient WebURL -> GURL conversions

This CL adds a constructor to GURL that takes a std::string instead of a char*
and a length. This constructor allows Blink to produce a temporary std::string
containing the URL's spec that we can move directly into the GURL, avoiding a
copy.

Once I update Blink, this constructor will help us avoid spending 5% of our
total time rendering http://sina.com.cn on KURL -> GURL conversions.

R=brettw
BUG=261412
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=213885

[Jeffrey Yasskin, 2013-07-24 21:36:21]

lgtm. Oh there's the GURL constructor I was missing in WebURL.

[abarth-chromium, 2013-07-24 21:56:47]

Sorry, I should cross-link the CLs.  The Blink side is in
https://codereview.chromium.org/20135002/.

[abarth-chromium, 2013-07-24 22:18:38]

@brettw: I believe I need your approval to land this GURL change.  Thanks!

[brettw, 2013-07-25 19:34:46]

LGTM if you can add a bit more clarity about swapping to the header (otherwise
it's not clear why passing by value is reasonable here).

[abarth-chromium, 2013-07-25 19:40:43]

Thanks and done.

[commit-bot: I haz the power, 2013-07-25 20:57:42]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/abarth@chromium.org/20127002/17001

[commit-bot: I haz the power, 2013-07-26 02:22:51]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/abarth@chromium.org/20127002/17001

[commit-bot: I haz the power, 2013-07-26 13:30:11]

Change committed as 213885