Revert of Unconditionally include <string> and <iostream> in json_reader.cpp...

Revert of Unconditionally include <string> and <iostream> in json_reader.cpp (https://codereview.chromium.org/291803003/)

Reason for revert:
This adds a static initializer.

Original issue's description:
> Unconditionally include <string> and <iostream> in json_reader.cpp
> Non-PNaCl builds that use libc++ also require these headers.
> 
> BUG=None
> R=mallinath@chromium.org
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=271429

TBR=mallinath@chromium.org,ronghuawu@chromium.org,glider@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=None

Review URL: https://codereview.chromium.org/290923003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271446 0039d316-1c4b-4281-b951-d872f2087c98

third_party/jsoncpp/overrides/src/lib_json/json_reader.cpp

@@ -14,14 +14,16 @@
 #include <cassert>
 #include <cstring>
 #include <stdexcept>
+#ifdef __pnacl__
 // This file uses the following headers (at least in Reader::parse), but
 // the upstream version doesn't include them because iostream pulls in
-// static initializers.  This breaks builds that use libc++ (including PNaCl),
-// because libc++ declares getline in <string> (as per the C++ standard)
+// static initializers.  This breaks the PNaCl build because it uses
+// libc++ which declares getline in <string> (as per the C++ standard)
 // but defines it in <iostream>. The code therefore fails linking, which
 // these includes fix.
 #include <string>
 #include <iostream>
+#endif
 
 #if _MSC_VER >= 1400 // VC++ 8.0
 #pragma warning( disable : 4996 )   // disable warning about strdup being deprecated.