diff --git a/src/libraries/System.Private.CoreLib/src/Resources/Strings.resx b/src/libraries/System.Private.CoreLib/src/Resources/Strings.resx
index 7fbe6aa096382..397893e8bf03a 100644
--- a/src/libraries/System.Private.CoreLib/src/Resources/Strings.resx
+++ b/src/libraries/System.Private.CoreLib/src/Resources/Strings.resx
@@ -1,17 +1,17 @@
 <?xml version="1.0" encoding="utf-8"?>
 <root>
-  <!-- 
-    Microsoft ResX Schema 
-    
+  <!--
+    Microsoft ResX Schema
+
     Version 2.0
-    
-    The primary goals of this format is to allow a simple XML format 
-    that is mostly human readable. The generation and parsing of the 
-    various data types are done through the TypeConverter classes 
+
+    The primary goals of this format is to allow a simple XML format
+    that is mostly human readable. The generation and parsing of the
+    various data types are done through the TypeConverter classes
     associated with the data types.
-    
+
     Example:
-    
+
     ... ado.net/XML headers & schema ...
     <resheader name="resmimetype">text/microsoft-resx</resheader>
     <resheader name="version">2.0</resheader>
@@ -26,36 +26,36 @@
         <value>[base64 mime encoded string representing a byte array form of the .NET Framework object]</value>
         <comment>This is a comment</comment>
     </data>
-                
-    There are any number of "resheader" rows that contain simple 
+
+    There are any number of "resheader" rows that contain simple
     name/value pairs.
-    
-    Each data row contains a name, and value. The row also contains a 
-    type or mimetype. Type corresponds to a .NET class that support 
-    text/value conversion through the TypeConverter architecture. 
-    Classes that don't support this are serialized and stored with the 
+
+    Each data row contains a name, and value. The row also contains a
+    type or mimetype. Type corresponds to a .NET class that support
+    text/value conversion through the TypeConverter architecture.
+    Classes that don't support this are serialized and stored with the
     mimetype set.
-    
-    The mimetype is used for serialized objects, and tells the 
-    ResXResourceReader how to depersist the object. This is currently not 
+
+    The mimetype is used for serialized objects, and tells the
+    ResXResourceReader how to depersist the object. This is currently not
     extensible. For a given mimetype the value must be set accordingly:
-    
-    Note - application/x-microsoft.net.object.binary.base64 is the format 
-    that the ResXResourceWriter will generate, however the reader can 
+
+    Note - application/x-microsoft.net.object.binary.base64 is the format
+    that the ResXResourceWriter will generate, however the reader can
     read any of the formats listed below.
-    
+
     mimetype: application/x-microsoft.net.object.binary.base64
-    value   : The object must be serialized with 
+    value   : The object must be serialized with
             : System.Runtime.Serialization.Formatters.Binary.BinaryFormatter
             : and then encoded with base64 encoding.
-    
+
     mimetype: application/x-microsoft.net.object.soap.base64
-    value   : The object must be serialized with 
+    value   : The object must be serialized with
             : System.Runtime.Serialization.Formatters.Soap.SoapFormatter
             : and then encoded with base64 encoding.
 
     mimetype: application/x-microsoft.net.object.bytearray.base64
-    value   : The object must be serialized into a byte array 
+    value   : The object must be serialized into a byte array
             : using a System.ComponentModel.TypeConverter
             : and then encoded with base64 encoding.
     -->
@@ -4337,4 +4337,10 @@
   <data name="Argument_BadArrayForInitializeArray" xml:space="preserve">
     <value>Only array or span of primitive or enum types can be initialized from static data.</value>
   </data>
+  <data name="CantGetAllPids" xml:space="preserve">
+    <value>Could not get all running Process IDs.</value>
+  </data>
+  <data name="RUsageFailure" xml:space="preserve">
+    <value>Failed to set or retrieve rusage information. See the error code for OS-specific error information.</value>
+  </data>
 </root>
diff --git a/src/libraries/System.Private.CoreLib/src/System/Environment.Browser.cs b/src/libraries/System.Private.CoreLib/src/System/Environment.Browser.cs
index 75a2633e67e34..4815ef73615b0 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Environment.Browser.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Environment.Browser.cs
@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.IO;
+using System.Runtime.Versioning;
 
 namespace System
 {
diff --git a/src/libraries/System.Private.CoreLib/src/System/Environment.OSX.cs b/src/libraries/System.Private.CoreLib/src/System/Environment.OSX.cs
index 82b6345ff40e1..c13a975b198d8 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Environment.OSX.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Environment.OSX.cs
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Diagnostics;
 using System.Runtime.InteropServices;
 using System.Runtime.Versioning;
 
@@ -26,6 +27,8 @@ public static ProcessCpuUsage CpuUsage
             }
         }
 
+        private const int NanosecondsTo100NanosecondsFactor = 100;
+
         private static volatile uint s_timeBase_numer, s_timeBase_denom;
         private static TimeSpan MapTime(ulong sysTime)
         {
diff --git a/src/libraries/System.Private.CoreLib/src/System/Environment.iOS.cs b/src/libraries/System.Private.CoreLib/src/System/Environment.iOS.cs
index 58a85227101bc..b6bd6a16bdb7d 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Environment.iOS.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Environment.iOS.cs
@@ -25,7 +25,7 @@ public static partial class Environment
         [UnsupportedOSPlatform("tvos")]
         public static ProcessCpuUsage CpuUsage
         {
-            get { throw new PlatformNotSupportedException(); }
+            get => new ProcessCpuUsage { UserTime = TimeSpan.Zero, PrivilegedTime = TimeSpan.Zero };
         }
 #endif