Use StringView for String::append and ::insert.

third_party/WebKit/Source/modules/encryptedmedia/HTMLMediaElementEncryptedMedia.cpp

 // Copyright 2014 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 "modules/encryptedmedia/HTMLMediaElementEncryptedMedia.h"
 
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "bindings/core/v8/ScriptState.h"
@@ skipping 71 matching lines @@
     void completeWithSession(WebContentDecryptionModuleResult::SessionStatus status) override
     {
         NOTREACHED();
         (*m_failureCallback)(InvalidStateError, "Unexpected completion.");
     }
 
     void completeWithError(WebContentDecryptionModuleException code, unsigned long systemCode, const WebString& message) override
     {
         // Non-zero |systemCode| is appended to the |message|. If the |message|
         // is empty, we'll report "Rejected with system code (systemCode)".
-        String errorString = message;
+        StringBuilder result;
+        result.append(message);
         if (systemCode != 0) {
-            if (errorString.isEmpty())
-                errorString.append("Rejected with system code");
-            errorString.append(" (" + String::number(systemCode) + ")");
+            if (result.isEmpty())
+                result.append("Rejected with system code");
+            result.append(" (");
+            result.appendNumber(systemCode);
+            result.append(')');
         }
-        (*m_failureCallback)(WebCdmExceptionToExceptionCode(code), errorString);
+        (*m_failureCallback)(WebCdmExceptionToExceptionCode(code), result.toString());
     }
 
 private:
     std::unique_ptr<SuccessCallback> m_successCallback;
     std::unique_ptr<FailureCallback> m_failureCallback;
 };
 
 ScriptPromise SetMediaKeysHandler::create(ScriptState* scriptState, HTMLMediaElement& element, MediaKeys* mediaKeys)
 {
     SetMediaKeysHandler* handler = new SetMediaKeysHandler(scriptState, element, mediaKeys);
@@ skipping 299 matching lines @@
 }
 
 DEFINE_TRACE(HTMLMediaElementEncryptedMedia)
 {
     visitor->trace(m_mediaElement);
     visitor->trace(m_mediaKeys);
     Supplement<HTMLMediaElement>::trace(visitor);
 }
 
 } // namespace blink