Move JoinString to the base namespace.

Change "Separator" from string to StringPIece (most are constants). Remove char versions for symmetry with SplitString.

Update callers who pass empty separators to use a base::StringPiece()

Change chromecast/base/metrics/cast_metrics_helper.cc to not use JoinString at all and just append to the output (code is simpler and faster).

TBR=zelidrag@chromium.org for chromeos

Committed: https://crrev.com/0eabfa001ba06d3c66992b95b69a988ef0633992
Cr-Commit-Position: refs/heads/master@{#338762}

patch from issue 1223153003 at patchset 160001 (http://crrev.com/1223153003#ps160001)

BUG=

Review URL: https://codereview.chromium.org/1230243005

Cr-Commit-Position: refs/heads/master@{#338819}

1 files changed, 6 insertions, 4 deletions

diff --git a/extensions/browser/api/vpn_provider/vpn_provider_api.cc b/extensions/browser/api/vpn_provider/vpn_provider_api.cc
index 069f171..e3b80ae 100644
--- a/extensions/browser/api/vpn_provider/vpn_provider_api.cc
+++ b/extensions/browser/api/vpn_provider/vpn_provider_api.cc
@@ -112,13 +112,14 @@ void ConvertParameters(const api_vpn::Parameters& parameters,
   parameter_value->SetStringWithoutPathExpansion(
       shill::kSubnetPrefixParameterThirdPartyVpn, cidr_parts[1]);
 
+  std::string ip_delimiter(1, shill::kIPDelimiter);
   parameter_value->SetStringWithoutPathExpansion(
       shill::kExclusionListParameterThirdPartyVpn,
-      JoinString(parameters.exclusion_list, shill::kIPDelimiter));
+      base::JoinString(parameters.exclusion_list, ip_delimiter));
 
   parameter_value->SetStringWithoutPathExpansion(
       shill::kInclusionListParameterThirdPartyVpn,
-      JoinString(parameters.inclusion_list, shill::kIPDelimiter));
+      base::JoinString(parameters.inclusion_list, ip_delimiter));
 
   if (parameters.mtu) {
     parameter_value->SetStringWithoutPathExpansion(
@@ -131,15 +132,16 @@ void ConvertParameters(const api_vpn::Parameters& parameters,
         *parameters.broadcast_address);
   }
 
+  std::string non_ip_delimiter(1, shill::kNonIPDelimiter);
   if (parameters.domain_search) {
     parameter_value->SetStringWithoutPathExpansion(
         shill::kDomainSearchParameterThirdPartyVpn,
-        JoinString(*parameters.domain_search, shill::kNonIPDelimiter));
+        base::JoinString(*parameters.domain_search, non_ip_delimiter));
   }
 
   parameter_value->SetStringWithoutPathExpansion(
       shill::kDnsServersParameterThirdPartyVpn,
-      JoinString(parameters.dns_servers, shill::kIPDelimiter));
+      base::JoinString(parameters.dns_servers, ip_delimiter));
 
   return;
 }