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, 4 insertions, 3 deletions

diff --git a/components/translate/core/browser/translate_prefs.cc b/components/translate/core/browser/translate_prefs.cc
index 768be0e..24547005 100644
--- a/components/translate/core/browser/translate_prefs.cc
+++ b/components/translate/core/browser/translate_prefs.cc
@@ -326,7 +326,7 @@ void TranslatePrefs::GetLanguageList(std::vector<std::string>* languages) {
 void TranslatePrefs::UpdateLanguageList(
     const std::vector<std::string>& languages) {
 #if defined(OS_CHROMEOS)
-  std::string languages_str = JoinString(languages, ',');
+  std::string languages_str = base::JoinString(languages, ",");
   prefs_->SetString(preferred_languages_pref_.c_str(), languages_str);
 #endif
 
@@ -335,7 +335,7 @@ void TranslatePrefs::UpdateLanguageList(
   // some web sites don't understand 'en-US' but 'en'. See crosbug.com/9884.
   std::vector<std::string> accept_languages;
   ExpandLanguageCodes(languages, &accept_languages);
-  std::string accept_languages_str = JoinString(accept_languages, ',');
+  std::string accept_languages_str = base::JoinString(accept_languages, ",");
   prefs_->SetString(accept_languages_pref_.c_str(), accept_languages_str);
 }
 
@@ -485,7 +485,8 @@ void TranslatePrefs::MigrateUserPrefs(PrefService* user_prefs,
         accept_languages.push_back(lang);
     }
 
-    std::string new_accept_languages_str = JoinString(accept_languages, ",");
+    std::string new_accept_languages_str =
+        base::JoinString(accept_languages, ",");
     user_prefs->SetString(accept_languages_pref, new_accept_languages_str);
   }
 }