Skip base::string16 if not necessary for WebString <-> ASCII conversion

media/blink/webcontentdecryptionmodulesession_impl.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "webcontentdecryptionmodulesession_impl.h"
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "base/logging.h"
 #include "base/numerics/safe_conversions.h"
@@ skipping 150 matching lines @@
   NOTREACHED();
   error_message->assign("Initialization data type is not supported.");
   return false;
 }
 
 static bool SanitizeSessionId(const blink::WebString& session_id,
                               std::string* sanitized_session_id) {
   // The user agent should thoroughly validate the sessionId value before
   // passing it to the CDM. At a minimum, this should include checking that
   // the length and value (e.g. alphanumeric) are reasonable.
-  if (!base::IsStringASCII(session_id))
+  if (!session_id.containsOnlyASCII())
     return false;
 
-  sanitized_session_id->assign(
-      base::UTF16ToASCII(base::StringPiece16(session_id)));
+  sanitized_session_id->assign(session_id.ascii());
   if (sanitized_session_id->length() > limits::kMaxSessionIdLength)
     return false;
 
   for (const char c : *sanitized_session_id) {
     if (!base::IsAsciiAlpha(c) && !base::IsAsciiDigit(c))
       return false;
   }
 
   return true;
 }
@@ skipping 279 matching lines @@
 
   DCHECK(session_id_.empty()) << "Session ID may not be changed once set.";
   session_id_ = session_id;
   *status =
       adapter_->RegisterSession(session_id_, weak_ptr_factory_.GetWeakPtr())
           ? SessionInitStatus::NEW_SESSION
           : SessionInitStatus::SESSION_ALREADY_EXISTS;
 }
 
 }  // namespace media