Remove duplicate implementations of string conversion methods.

BUG=webrtc:4773

Review-Url: https://codereview.webrtc.org/2583853002
Cr-Commit-Position: refs/heads/master@{#15957}

webrtc/sdk/objc/Framework/Classes/helpers.h

@@ -20,6 +20,7 @@ namespace ios {
 
 bool CheckAndLogError(BOOL success, NSError* error);
 
+NSString *NSStringFromStdString(const std::string& stdString);
 std::string StdStringFromNSString(NSString* nsString);
 
 // Return thread ID as a string.

webrtc/test/BUILD.gn

@@ -166,6 +166,10 @@ rtc_source_set("test_support") {
     deps += [ "//base:base" ]
   }
 
+  if (is_ios) {
+    deps += [ "//webrtc/sdk:rtc_sdk_common_objc" ]
+  }
+
   if (rtc_use_memcheck) {
     data = valgrind_webrtc_dependencies
   }

webrtc/test/DEPS

@@ -12,6 +12,7 @@ include_rules = [
   "+webrtc/modules/rtp_rtcp",
   "+webrtc/modules/video_capture",
   "+webrtc/modules/video_coding",
+  "+webrtc/sdk",
   "+webrtc/system_wrappers",
   "+webrtc/voice_engine",
 ]

webrtc/test/testsupport/iosfileutils.mm

@@ -19,25 +19,13 @@
 
 #include "webrtc/base/checks.h"
 #include "webrtc/typedefs.h"
+#include "webrtc/sdk/objc/Framework/Classes/helpers.h"
 
 namespace webrtc {
 namespace test {
 
-// TODO(henrika): move to shared location.
-// See https://code.google.com/p/webrtc/issues/detail?id=4773 for details.
-NSString* NSStringFromStdString(const std::string& stdString) {
-  // std::string may contain null termination character so we construct
-  // using length.
-  return [[NSString alloc] initWithBytes:stdString.data()
-                                  length:stdString.length()
-                                encoding:NSUTF8StringEncoding];
-}
-
-std::string StdStringFromNSString(NSString* nsString) {
-  NSData* charData = [nsString dataUsingEncoding:NSUTF8StringEncoding];
-  return std::string(reinterpret_cast<const char*>([charData bytes]),
-                     [charData length]);
-}
+using webrtc::ios::NSStringFromStdString;
+using webrtc::ios::StdStringFromNSString;
 
 // For iOS, resource files are added to the application bundle in the root
 // and not in separate folders as is the case for other platforms. This method