Make SimpleStringBuilder into a non-template

So that future CLs can de-inline its methods.

We do this by asking the caller to allocate the buffer instead of
having it as a data member.

Bug: webrtc:8982
Change-Id: I246b0973e54510fdd880c3b6875336c31334d008
Reviewed-on: https://webrtc-review.googlesource.com/60000
Commit-Queue: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Fredrik Solenberg <solenberg@webrtc.org>
Reviewed-by: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22355}
diff --git a/rtc_base/logging.cc b/rtc_base/logging.cc
index 4798f4d..ec8cd7f 100644
--- a/rtc_base/logging.cc
+++ b/rtc_base/logging.cc
@@ -127,7 +127,8 @@
     print_stream_ << "(" << FilenameFromPath(file)  << ":" << line << "): ";
 
   if (err_ctx != ERRCTX_NONE) {
-    SimpleStringBuilder<1024> tmp;
+    char tmp_buf[1024];
+    SimpleStringBuilder tmp(tmp_buf);
     tmp.AppendFormat("[0x%08X]", err);
     switch (err_ctx) {
       case ERRCTX_ERRNO: