No need to stop the one shot timer once the timer fired.

third_party/WebKit/Source/modules/payments/PaymentRequest.cpp

 // Copyright 2016 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/payments/PaymentRequest.h"
 
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/JSONValuesForV8.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/modules/v8/V8PaymentDetails.h"
 #include "core/EventTypeNames.h"
 #include "core/dom/DOMException.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/events/Event.h"
 #include "core/events/EventQueue.h"
 #include "modules/EventTargetModulesNames.h"
 #include "modules/payments/PaymentAddress.h"
 #include "modules/payments/PaymentItem.h"
 #include "modules/payments/PaymentRequestUpdateEvent.h"
 #include "modules/payments/PaymentResponse.h"
 #include "modules/payments/PaymentShippingOption.h"
 #include "modules/payments/PaymentsValidators.h"
 #include "mojo/public/cpp/bindings/interface_request.h"
 #include "mojo/public/cpp/bindings/wtf_array.h"
 #include "platform/mojo/MojoHelper.h"
 #include "public/platform/InterfaceProvider.h"
+#include "public/platform/WebTraceLocation.h"

[please use gerrit instead, 2016/08/08 16:35:58]

Why was this include added?

[pals, 2016/08/09 01:53:09]

Its for the BLINK_FROM_HERE.

 #include "wtf/HashSet.h"
 #include <utility>
 
 namespace mojo {
 
 using blink::mojom::blink::PaymentCurrencyAmount;
 using blink::mojom::blink::PaymentCurrencyAmountPtr;
 using blink::mojom::blink::PaymentDetails;
 using blink::mojom::blink::PaymentDetailsModifier;
 using blink::mojom::blink::PaymentDetailsModifierPtr;
@@ skipping 443 matching lines @@
     visitor->trace(m_shippingAddress);
     visitor->trace(m_showResolver);
     visitor->trace(m_completeResolver);
     visitor->trace(m_abortResolver);
     EventTargetWithInlineData::trace(visitor);
     ContextLifecycleObserver::trace(visitor);
 }
 
 void PaymentRequest::onCompleteTimeoutForTesting()
 {
+    m_completeTimer.stop();
     onCompleteTimeout(0);
 }
 
 PaymentRequest::PaymentRequest(ScriptState* scriptState, const HeapVector<PaymentMethodData>& methodData, const PaymentDetails& details, const PaymentOptions& options, ExceptionState& exceptionState)
     : ContextLifecycleObserver(scriptState->getExecutionContext())
     , ActiveScriptWrappable(this)
     , m_options(options)
     , m_clientBinding(this)
     , m_completeTimer(this, &PaymentRequest::onCompleteTimeout)
 {
@@ skipping 178 matching lines @@
         return;
     }
 
     m_showResolver->reject(DOMException::create(AbortError));
     m_abortResolver->resolve();
     clearResolversAndCloseMojoConnection();
 }
 
 void PaymentRequest::onCompleteTimeout(TimerBase*)
 {
-    m_completeTimer.stop();
     m_paymentProvider->Complete(mojom::blink::PaymentComplete(Fail));
     clearResolversAndCloseMojoConnection();
 }
 
 void PaymentRequest::clearResolversAndCloseMojoConnection()
 {
     m_completeResolver.clear();
     m_showResolver.clear();
     m_abortResolver.clear();
     if (m_clientBinding.is_bound())
         m_clientBinding.Close();
     m_paymentProvider.reset();
 }
 
 } // namespace blink