Replace std::unique_ptr.reset() with WrapUnique assignment.

fpdfsdk/ edition.

Review-Url: https://codereview.chromium.org/2381723002
diff --git a/fpdfsdk/javascript/JS_Runtime_Stub.cpp b/fpdfsdk/javascript/JS_Runtime_Stub.cpp
index 2c7eda8..3b316aa 100644
--- a/fpdfsdk/javascript/JS_Runtime_Stub.cpp
+++ b/fpdfsdk/javascript/JS_Runtime_Stub.cpp
@@ -124,7 +124,7 @@
 
   IJS_Context* NewContext() override {
     if (!m_pContext)
-      m_pContext.reset(new CJS_ContextStub());
+      m_pContext = WrapUnique(new CJS_ContextStub());
     return GetCurrentContext();
   }