Fix variable shadowing warning in registry on VS2015

d:\src\cr3\src\base\win\registry.cc(665): error C2220: warning treated as error - no 'object' file generated
d:\src\cr3\src\base\win\registry.cc(665): warning C4456: declaration of 'result' hides previous local declaration
d:\src\cr3\src\base\win\registry.cc(659): note: see declaration of 'result'

I don't think there's any need for separate variables.

R=cpu@chromium.org
BUG=440500

Review URL: https://codereview.chromium.org/868253004

Cr-Commit-Position: refs/heads/master@{#313373}

base/win/registry.cc

@@ -662,8 +662,8 @@ void RegistryKeyIterator::Initialize(HKEY root_key,
     key_ = NULL;
   } else {
     DWORD count = 0;
-    LONG result = ::RegQueryInfoKey(key_, NULL, 0, NULL, &count, NULL, NULL,
-                                    NULL, NULL, NULL, NULL, NULL);
+    result = ::RegQueryInfoKey(key_, NULL, 0, NULL, &count, NULL, NULL, NULL,
+                               NULL, NULL, NULL, NULL);
 
     if (result != ERROR_SUCCESS) {
       ::RegCloseKey(key_);