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}

8 files changed, 20 insertions, 57 deletions

diff --git a/base/debug/crash_logging.cc b/base/debug/crash_logging.cc
index f9b4449..058b476 100644
--- a/base/debug/crash_logging.cc
+++ b/base/debug/crash_logging.cc
@@ -119,7 +119,7 @@ void SetCrashKeyFromAddresses(const base::StringPiece& key,
       hex_backtrace.push_back(s);
     }
 
-    value = JoinString(hex_backtrace, ' ');
+    value = base::JoinString(hex_backtrace, " ");
 
     // Warn if this exceeds the breakpad limits.
     DCHECK_LE(value.length(), kBreakpadValueMax);
diff --git a/base/strings/string_util.cc b/base/strings/string_util.cc
index ae5fb80..a0c95ec 100644
--- a/base/strings/string_util.cc
+++ b/base/strings/string_util.cc
@@ -884,43 +884,36 @@ char16* WriteInto(base::string16* str, size_t length_with_null) {
   return WriteIntoT(str, length_with_null);
 }
 
-}  // namespace base
-
 template<typename STR>
-static STR JoinStringT(const std::vector<STR>& parts, const STR& sep) {
+static STR JoinStringT(const std::vector<STR>& parts,
+                       BasicStringPiece<STR> sep) {
   if (parts.empty())
     return STR();
 
   STR result(parts[0]);
-  typename std::vector<STR>::const_iterator iter = parts.begin();
+  auto iter = parts.begin();
   ++iter;
 
   for (; iter != parts.end(); ++iter) {
-    result += sep;
+    sep.AppendToString(&result);
     result += *iter;
   }
 
   return result;
 }
 
-std::string JoinString(const std::vector<std::string>& parts, char sep) {
-  return JoinStringT(parts, std::string(1, sep));
-}
-
-string16 JoinString(const std::vector<string16>& parts, char16 sep) {
-  return JoinStringT(parts, string16(1, sep));
-}
-
 std::string JoinString(const std::vector<std::string>& parts,
-                       const std::string& separator) {
+                       StringPiece separator) {
   return JoinStringT(parts, separator);
 }
 
 string16 JoinString(const std::vector<string16>& parts,
-                    const string16& separator) {
+                    StringPiece16 separator) {
   return JoinStringT(parts, separator);
 }
 
+}  // namespace base
+
 template<class FormatStringType, class OutStringType>
 OutStringType DoReplaceStringPlaceholders(const FormatStringType& format_string,
     const std::vector<OutStringType>& subst, std::vector<size_t>* offsets) {
diff --git a/base/strings/string_util.h b/base/strings/string_util.h
index e4abce2..b75a9f88 100644
--- a/base/strings/string_util.h
+++ b/base/strings/string_util.h
@@ -491,6 +491,12 @@ BASE_EXPORT char16* WriteInto(base::string16* str, size_t length_with_null);
 BASE_EXPORT wchar_t* WriteInto(std::wstring* str, size_t length_with_null);
 #endif
 
+// Does the opposite of SplitString().
+BASE_EXPORT std::string JoinString(const std::vector<std::string>& parts,
+                                   StringPiece separator);
+BASE_EXPORT string16 JoinString(const std::vector<string16>& parts,
+                                StringPiece16 separator);
+
 }  // namespace base
 
 #if defined(OS_WIN)
@@ -501,22 +507,6 @@ BASE_EXPORT wchar_t* WriteInto(std::wstring* str, size_t length_with_null);
 #error Define string operations appropriately for your platform
 #endif
 
-//-----------------------------------------------------------------------------
-
-// Does the opposite of SplitString().
-BASE_EXPORT base::string16 JoinString(const std::vector<base::string16>& parts,
-                                      base::char16 s);
-BASE_EXPORT std::string JoinString(
-    const std::vector<std::string>& parts, char s);
-
-// Join |parts| using |separator|.
-BASE_EXPORT std::string JoinString(
-    const std::vector<std::string>& parts,
-    const std::string& separator);
-BASE_EXPORT base::string16 JoinString(
-    const std::vector<base::string16>& parts,
-    const base::string16& separator);
-
 // Replace $1-$2-$3..$9 in the format string with |a|-|b|-|c|..|i| respectively.
 // Additionally, any number of consecutive '$' characters is replaced by that
 // number less one. Eg $$->$, $$$->$$, etc. The offsets parameter here can be
diff --git a/base/strings/string_util_unittest.cc b/base/strings/string_util_unittest.cc
index 1593f81..5d5ba8b 100644
--- a/base/strings/string_util_unittest.cc
+++ b/base/strings/string_util_unittest.cc
@@ -669,26 +669,7 @@ TEST(StringUtilTest, HexDigitToInt) {
   EXPECT_EQ(15, HexDigitToInt('f'));
 }
 
-// Test for JoinString
 TEST(StringUtilTest, JoinString) {
-  std::vector<std::string> in;
-  EXPECT_EQ("", JoinString(in, ','));
-
-  in.push_back("a");
-  EXPECT_EQ("a", JoinString(in, ','));
-
-  in.push_back("b");
-  in.push_back("c");
-  EXPECT_EQ("a,b,c", JoinString(in, ','));
-
-  in.push_back(std::string());
-  EXPECT_EQ("a,b,c,", JoinString(in, ','));
-  in.push_back(" ");
-  EXPECT_EQ("a|b|c|| ", JoinString(in, '|'));
-}
-
-// Test for JoinString overloaded with std::string separator
-TEST(StringUtilTest, JoinStringWithString) {
   std::string separator(", ");
   std::vector<std::string> parts;
   EXPECT_EQ(std::string(), JoinString(parts, separator));
@@ -706,8 +687,7 @@ TEST(StringUtilTest, JoinStringWithString) {
   EXPECT_EQ("a|b|c|| ", JoinString(parts, "|"));
 }
 
-// Test for JoinString overloaded with string16 separator
-TEST(StringUtilTest, JoinStringWithString16) {
+TEST(StringUtilTest, JoinString16) {
   string16 separator = ASCIIToUTF16(", ");
   std::vector<string16> parts;
   EXPECT_EQ(string16(), JoinString(parts, separator));
diff --git a/base/test/launcher/test_launcher.cc b/base/test/launcher/test_launcher.cc
index 2a56b6c..7c0bc4e 100644
--- a/base/test/launcher/test_launcher.cc
+++ b/base/test/launcher/test_launcher.cc
@@ -570,7 +570,7 @@ void TestLauncher::OnTestFinished(const TestResult& result) {
           snippet_lines.begin() + truncated_size);
       snippet_lines.insert(snippet_lines.begin(), "<truncated>");
     }
-    fprintf(stdout, "%s", JoinString(snippet_lines, "\n").c_str());
+    fprintf(stdout, "%s", base::JoinString(snippet_lines, "\n").c_str());
     fflush(stdout);
   }
 
diff --git a/base/test/launcher/test_launcher_ios.cc b/base/test/launcher/test_launcher_ios.cc
index ecd31ae..3179bb3 100644
--- a/base/test/launcher/test_launcher_ios.cc
+++ b/base/test/launcher/test_launcher_ios.cc
@@ -121,7 +121,7 @@ class IOSUnitTestPlatformDelegate : public base::UnitTestPlatformDelegate {
     base::CommandLine cmd_line(dir_exe_.AppendASCII(test_name_ + ".app"));
     cmd_line.AppendSwitchPath(switches::kTestLauncherOutput, output_file);
     cmd_line.AppendSwitchASCII(base::kGTestFilterFlag,
-                               JoinString(test_names, ":"));
+                               base::JoinString(test_names, ":"));
     return cmd_line;
   }
 
diff --git a/base/test/launcher/test_launcher_nacl_nonsfi.cc b/base/test/launcher/test_launcher_nacl_nonsfi.cc
index fa52604..bf117af 100644
--- a/base/test/launcher/test_launcher_nacl_nonsfi.cc
+++ b/base/test/launcher/test_launcher_nacl_nonsfi.cc
@@ -113,7 +113,7 @@ class NonSfiUnitTestPlatformDelegate : public base::UnitTestPlatformDelegate {
     cmd_line.AppendSwitchPath(
         switches::kTestLauncherOutput, output_file);
     cmd_line.AppendSwitchASCII(
-        base::kGTestFilterFlag, JoinString(test_names, ":"));
+        base::kGTestFilterFlag, base::JoinString(test_names, ":"));
     return cmd_line;
   }
 
diff --git a/base/trace_event/trace_event_impl.cc b/base/trace_event/trace_event_impl.cc
index f01a888..cd8cf4a 100644
--- a/base/trace_event/trace_event_impl.cc
+++ b/base/trace_event/trace_event_impl.cc
@@ -2352,7 +2352,7 @@ void TraceLog::AddMetadataEventsWhileLocked() {
     InitializeMetadataEvent(AddEventToThreadSharedChunkWhileLocked(NULL, false),
                             current_thread_id,
                             "process_labels", "labels",
-                            JoinString(labels, ','));
+                            base::JoinString(labels, ","));
   }
 
   // Thread sort indices.