Allow compiling the google-breakpad code using a global ::string class instead of std::string.

For more details take a look at common/using_std_string.h

BUG=

Change-Id: Ifebfc57f691ef3a3bef8cfed7106c567985edffc
Reviewed-on: https://chromium-review.googlesource.com/399738
Reviewed-by: Mark Mentovai <mark@chromium.org>

src/common/dwarf/elf_reader.h

@@ -19,8 +19,8 @@
 #include <vector>
 
 #include "common/dwarf/types.h"
+#include "common/using_std_string.h"
 
-using std::string;
 using std::vector;
 using std::pair;