Replace kEmptyString with OnceInit initialized string*

Replace kEmptyString with OnceInit initialized string*

This removes the global constructor call for std::string kEmptyString.

This is roughly an application of b/7549760 from the internal
version of protobuf.

Upstream patch here https://codereview.appspot.com/63480043/.

R=fischman@chromium.org
TBR=darin@chromium.org
BUG=341941, 94925
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=251212

[Ami GONE FROM CHROMIUM, 2014-02-13 23:45:54]

LGTM++

https://codereview.chromium.org/164743002/diff/60001/third_party/protobuf/src...
File third_party/protobuf/src/google/protobuf/generated_message_util.cc (right):

https://codereview.chromium.org/164743002/diff/60001/third_party/protobuf/src...
third_party/protobuf/src/google/protobuf/generated_message_util.cc:54:
empty_string_ = new std::string;
nit: s/;/();/

[scottmg, 2014-02-13 23:48:04]

https://codereview.chromium.org/164743002/diff/60001/third_party/protobuf/src...
File third_party/protobuf/src/google/protobuf/generated_message_util.cc (right):

https://codereview.chromium.org/164743002/diff/60001/third_party/protobuf/src...
third_party/protobuf/src/google/protobuf/generated_message_util.cc:54:
empty_string_ = new std::string;
On 2014/02/13 23:45:54, Ami Fischman wrote:
> nit: s/;/();/

Done.

[scottmg, 2014-02-13 23:50:43]

The CQ bit was checked by scottmg@chromium.org

[commit-bot: I haz the power, 2014-02-13 23:51:20]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/scottmg@chromium.org/164743002/170001

[commit-bot: I haz the power, 2014-02-14 00:20:12]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-02-14 00:20:13]

Retried try job too often on chromium_presubmit for step(s) presubmit
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=chromium_p...

[scottmg, 2014-02-14 00:26:49]

tbr darin for update to existing third_party/ code. tryjobs in ps#3.

[scottmg, 2014-02-14 00:50:44]

Committed patchset #4 manually as r251212 (presubmit successful).

[darin (slow to review), 2014-02-14 05:16:39]

LGTM