Implement SysInfo::HardwareModelName() on iOS.

base/sys_info_mac.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/sys_info.h"
 
 #include <ApplicationServices/ApplicationServices.h>
 #include <CoreServices/CoreServices.h>
 #import <Foundation/Foundation.h>
 #include <mach/mach_host.h>
@@ skipping 78 matching lines @@
     return 0;
   // We should add inactive file-backed memory also but there is no such
   // information from Mac OS unfortunately.
   return static_cast<int64_t>(info.free + info.speculative) * 1024;
 }
 
 // static
 std::string SysInfo::CPUModelName() {
   char name[256];
   size_t len = arraysize(name);
-  if (sysctlbyname("machdep.cpu.brand_string", &name, &len, NULL, 0) == 0)
-    return name;
+  if (sysctlbyname("machdep.cpu.brand_string", &name, &len, nullptr, 0) == 0) {
+    DCHECK_GE(len, 1u);
+    DCHECK_EQ('\0', name[len - 1]);
+    return std::string(name, len - 1);
+  }
   return std::string();
 }
 
+// static
 std::string SysInfo::HardwareModelName() {
   char model[256];
   size_t len = sizeof(model);
-  if (sysctlbyname("hw.model", model, &len, NULL, 0) == 0)
-    return std::string(model, 0, len);
+  if (sysctlbyname("hw.model", model, &len, nullptr, 0) == 0) {
+    DCHECK_GE(len, 1u);
+    DCHECK_EQ('\0', model[len - 1]);
+    return std::string(model, len - 1);
+  }
   return std::string();
 }
 
 }  // namespace base