Revert "Move webrtc/{base => rtc_base}" (https://codereview.webrtc.org/2877023002)

Will reland in two different commits to preserve git blame history.

BUG=webrtc:7634
NOTRY=True
TBR=kwiberg@webrtc.org

Change-Id: I550da8525aeb9c5b8f96338fcf1c9714f3dcdab1
Reviewed-on: https://chromium-review.googlesource.com/554610
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18820}

webrtc/base/stringize_macros.h

@@ -18,9 +18,21 @@
 #ifndef WEBRTC_BASE_STRINGIZE_MACROS_H_
 #define WEBRTC_BASE_STRINGIZE_MACROS_H_
 
+// This is not very useful as it does not expand defined symbols if
+// called directly. Use its counterpart without the _NO_EXPANSION
+// suffix, below.
+#define STRINGIZE_NO_EXPANSION(x) #x
 
-// This header is deprecated and is just left here temporarily during
-// refactoring. See https://bugs.webrtc.org/7634 for more details.
-#include "webrtc/rtc_base/stringize_macros.h"
+// Use this to quote the provided parameter, first expanding it if it
+// is a preprocessor symbol.
+//
+// For example, if:
+//   #define A FOO
+//   #define B(x) myobj->FunctionCall(x)
+//
+// Then:
+//   STRINGIZE(A) produces "FOO"
+//   STRINGIZE(B(y)) produces "myobj->FunctionCall(y)"
+#define STRINGIZE(x) STRINGIZE_NO_EXPANSION(x)
 
 #endif  // WEBRTC_BASE_STRINGIZE_MACROS_H_