Strip out unused reg code. (dotnet/coreclr#10741)

* Strip out unused reg code.

Removing the unused code to better be able to audit our CoreLib usage and to prepare for targeted code sharing with CoreFX. Wraps key usages in using statements.

* Fix static init and remove Contract

Signed-off-by: dotnet-bot-corefx-mirror <dotnet-bot@microsoft.com>

Author: JeremyKuhne

src/Common/src/CoreLib/System/Diagnostics/Tracing/EventProvider.cs

@@ -555,21 +555,21 @@ private unsafe bool GetDataFromController(int etwSessionId,
             {
 #if (!ES_BUILD_PCL && !ES_BUILD_PN && !FEATURE_PAL)
                 string regKey = @"\Microsoft\Windows\CurrentVersion\Winevt\Publishers\{" + m_providerId + "}";
-                if (System.Runtime.InteropServices.Marshal.SizeOf(typeof(IntPtr)) == 8)
-                    regKey = @"HKEY_LOCAL_MACHINE\Software" + @"\Wow6432Node" + regKey;
+                if (Marshal.SizeOf(typeof(IntPtr)) == 8)
+                    regKey = @"Software" + @"\Wow6432Node" + regKey;
                 else
-                    regKey = @"HKEY_LOCAL_MACHINE\Software" + regKey;
+                    regKey = @"Software" + regKey;
 
                 string valueName = "ControllerData_Session_" + etwSessionId.ToString(CultureInfo.InvariantCulture);
 
-                // we need to assert this permission for partial trust scenarios
-#if !CORECLR
-                (new RegistryPermission(RegistryPermissionAccess.Read, regKey)).Assert();
-#endif
-                data = Microsoft.Win32.Registry.GetValue(regKey, valueName, null) as byte[];
+                using (RegistryKey key = Registry.LocalMachine.OpenSubKey(regKey, writable: false))
+                {
+                    data = key.GetValue(valueName) as byte[];
+                }
+
                 if (data != null)
                 {
-                    // We only used the persisted data from the registry for updates.   
+                    // We only used the persisted data from the registry for updates.
                     command = ControllerCommand.Update;
                     return true;
                 }