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

third_party/WebKit/Source/modules/encryptedmedia/ContentDecryptionModuleResultPromise.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/ContentDecryptionModuleResultPromise.h"
 
 #include "bindings/core/v8/ScriptPromise.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "core/dom/DOMException.h"
 #include "core/dom/ExecutionContext.h"
@@ skipping 53 matching lines @@
 {
     NOTREACHED();
     reject(InvalidStateError, "Unexpected completion.");
 }
 
 void ContentDecryptionModuleResultPromise::completeWithError(WebContentDecryptionModuleException exceptionCode, unsigned long systemCode, const WebString& errorMessage)
 {
     // Non-zero |systemCode| is appended to the |errorMessage|. If the
     // |errorMessage| is empty, we'll report "Rejected with system code
     // (systemCode)".
-    String errorString = errorMessage;
+    StringBuilder result;
+    result.append(errorMessage);
     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(')');
     }
-    reject(WebCdmExceptionToExceptionCode(exceptionCode), errorString);
+    reject(WebCdmExceptionToExceptionCode(exceptionCode), result.toString());
 }
 
 ScriptPromise ContentDecryptionModuleResultPromise::promise()
 {
     return m_resolver->promise();
 }
 
 void ContentDecryptionModuleResultPromise::reject(ExceptionCode code, const String& errorMessage)
 {
     // Reject the promise asynchronously. This avoids problems when gc is
@@ skipping 16 matching lines @@
     return m_resolver->getExecutionContext();
 }
 
 DEFINE_TRACE(ContentDecryptionModuleResultPromise)
 {
     visitor->trace(m_resolver);
     ContentDecryptionModuleResult::trace(visitor);
 }
 
 } // namespace blink