Make GetUserName() return more specific error code, so that we could know how the function failed.

rlz/win/lib/process_info.cc

Index: rlz/win/lib/process_info.cc
diff --git a/rlz/win/lib/process_info.cc b/rlz/win/lib/process_info.cc
index 2511f54ab76ab3cefb12035ba5893e8a92ee1816..d17b4feb63483f584dce664f762670633884f300 100644
--- a/rlz/win/lib/process_info.cc
+++ b/rlz/win/lib/process_info.cc
@@ -33,8 +33,8 @@ HRESULT GetCurrentUser(std::wstring* name,
   // In which case, search for and use the process handle of a running
   // Explorer.exe.)
   HANDLE token;
-  if (!::OpenProcessToken(::GetCurrentProcess(), TOKEN_QUERY, &token))
-    return E_FAIL;
+
+  CHECK(::OpenProcessToken(::GetCurrentProcess(), TOKEN_QUERY, &token));
 
   base::win::ScopedHandle scoped_process_token(token);
 
@@ -49,13 +49,10 @@ HRESULT GetCurrentUser(std::wstring* name,
   CHECK(!result && err == ERROR_INSUFFICIENT_BUFFER);
 
   token_user_bytes.reset(new char[token_user_size]);
-  if (!token_user_bytes.get())
-    return E_OUTOFMEMORY;
+  CHECK(token_user_bytes.get());
 
-  if (!::GetTokenInformation(token, TokenUser, token_user_bytes.get(),
-                             token_user_size, &token_user_size2)) {
-    return E_FAIL;
-  }
+  CHECK(::GetTokenInformation(token, TokenUser, token_user_bytes.get(),
+                              token_user_size, &token_user_size2));
 
   WCHAR user_name[UNLEN + 1];  // max username length
   WCHAR domain_name[UNLEN + 1];
@@ -64,13 +61,11 @@ HRESULT GetCurrentUser(std::wstring* name,
   SID_NAME_USE sid_type;
   TOKEN_USER* token_user =
       reinterpret_cast<TOKEN_USER*>(token_user_bytes.get());
-  if (!token_user)
-    return E_FAIL;
+  CHECK(token_user);
+
   PSID user_sid = token_user->User.Sid;
-  if (!::LookupAccountSidW(NULL, user_sid, user_name, &user_name_size,
-                           domain_name, &domain_name_size, &sid_type)) {
-    return E_FAIL;
-  }
+  CHECK(::LookupAccountSidW(NULL, user_sid, user_name, &user_name_size,
+                            domain_name, &domain_name_size, &sid_type));
 
   if (name != NULL) {
     *name = user_name;