Bug 1344629 - Part 6: Rewrite unnecessary uses of nsLiteralString. r=dbaron

There's an antipattern where nsLiteralString is used as an unnecessary intermediary in converting from CharT* to CharT*,
e.g. CallAFunctionThatTakesACharPointer(NS_LITERAL_CSTRING("foo").get());
or
NS_NAMED_LITERAL_STRING(foo, "abc");
CallAFunctionThatTakesACharPointer(foo.get());

This patch rewrites the callsites that can be trivially changed to use char*/char16_t*.

I'd somewhat like to remove nsTLiteralString::get() altogether, but in code that's less straightforward than these examples, get() is useful enough to keep.

MozReview-Commit-ID: Kh1rUziVllo

xpcom/base/nsSystemInfo.cpp

@@ -183,9 +183,7 @@ nsresult GetInstallYear(uint32_t& aYear)
 {
   HKEY hKey;
   LONG status = RegOpenKeyExW(HKEY_LOCAL_MACHINE,
-                              NS_LITERAL_STRING(
-                              "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion"
-                              ).get(),
+                              L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion",
                               0, KEY_READ | KEY_WOW64_64KEY, &hKey);
 
   if (status != ERROR_SUCCESS) {