Fix GMOCK WARNING: Uninteresting mock function call - taking default action.

BUG=587995

Review-Url: https://codereview.chromium.org/2175613003
Cr-Commit-Position: refs/heads/master@{#407193}

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

@@ -157,6 +157,7 @@ PaymentRequestMockFunctionScope::~PaymentRequestMockFunctionScope()
 v8::Local<v8::Function> PaymentRequestMockFunctionScope::expectCall(String* captor)
 {
     m_mockFunctions.append(new MockFunction(m_scriptState, captor));
+    EXPECT_CALL(*m_mockFunctions.last(), call(testing::_));
     return m_mockFunctions.last()->bind();
 }