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, 2 insertions, 2 deletions

diff --git a/chromeos/network/onc/onc_validator.cc b/chromeos/network/onc/onc_validator.cc
index 4e2e732..4c2067a 100644
--- a/chromeos/network/onc/onc_validator.cc
+++ b/chromeos/network/onc/onc_validator.cc
@@ -325,7 +325,7 @@ std::string JoinStringRange(const std::vector<const char*>& strings,
                             const std::string& separator) {
   std::vector<std::string> string_vector;
   std::copy(strings.begin(), strings.end(), std::back_inserter(string_vector));
-  return JoinString(string_vector, separator);
+  return base::JoinString(string_vector, separator);
 }
 
 }  // namespace
@@ -952,7 +952,7 @@ bool Validator::ValidateCertificate(base::DictionaryValue* result) {
 }
 
 std::string Validator::MessageHeader() {
-  std::string path = path_.empty() ? "toplevel" : JoinString(path_, ".");
+  std::string path = path_.empty() ? "toplevel" : base::JoinString(path_, ".");
   std::string message = "At " + path + ": ";
   return message;
 }