Revert of Move JoinString to the base namespace

ui/message_center/views/bounded_label.cc

Index: ui/message_center/views/bounded_label.cc
diff --git a/ui/message_center/views/bounded_label.cc b/ui/message_center/views/bounded_label.cc
index f9f6ffb6bc3dc431bcc131fc74de955cede72710..5bf6f151eec88bb0cf5e43d633645ca55a8d29bf 100644
--- a/ui/message_center/views/bounded_label.cc
+++ b/ui/message_center/views/bounded_label.cc
@@ -113,10 +113,10 @@
                                    std::max(width - insets.width(), 0);
     int text_height = std::numeric_limits<int>::max();
     std::vector<base::string16> wrapped = GetWrappedText(text_width, lines);
-    gfx::Canvas::SizeStringInt(
-        base::JoinString(wrapped, base::ASCIIToUTF16("\n")),
-        font_list(), &text_width, &text_height, owner_->GetLineHeight(),
-        GetTextFlags());
+    gfx::Canvas::SizeStringInt(JoinString(wrapped, '\n'), font_list(),
+                               &text_width, &text_height,
+                               owner_->GetLineHeight(),
+                               GetTextFlags());
     size.set_width(text_width + insets.width());
     size.set_height(text_height + insets.height());
     SetCachedSize(key, size);
@@ -177,8 +177,7 @@
     gfx::Rect bounds(width(), height);
     bounds.Inset(owner_->GetInsets());
     if (bounds.width() != wrapped_text_width_ || lines != wrapped_text_lines_) {
-      wrapped_text_ = base::JoinString(GetWrappedText(bounds.width(), lines),
-                                       base::ASCIIToUTF16("\n"));
+      wrapped_text_ = JoinString(GetWrappedText(bounds.width(), lines), '\n');
       wrapped_text_width_ = bounds.width();
       wrapped_text_lines_ = lines;
     }
@@ -344,8 +343,7 @@
 }
 
 base::string16 BoundedLabel::GetWrappedTextForTest(int width, int lines) {
-  return base::JoinString(label_->GetWrappedText(width, lines),
-                          base::ASCIIToUTF16("\n"));
+  return JoinString(label_->GetWrappedText(width, lines), '\n');
 }
 
 }  // namespace message_center