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

dom/html/ImageDocument.cpp

@@ -585,8 +585,7 @@ ImageDocument::OnLoadComplete(imgIRequest* aRequest, nsresult aStatus)
     NS_ConvertUTF8toUTF16 srcString(src);
     const char16_t* formatString[] = { srcString.get() };
     nsXPIDLString errorMsg;
-    NS_NAMED_LITERAL_STRING(str, "InvalidImage");
-    mStringBundle->FormatStringFromName(str.get(), formatString, 1,
+    mStringBundle->FormatStringFromName(u"InvalidImage", formatString, 1,
                                         getter_Copies(errorMsg));
 
     mImageContent->SetAttr(kNameSpaceID_None, nsGkAtoms::alt, errorMsg, false);