Add some calls to MakeUnique

This CL replaces some new's with pdfium::MakeUnique.

Change-Id: I50faf3ed55e7730b094c14a7989a9dd51cf33cbb
Reviewed-on: https://pdfium-review.googlesource.com/3430
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/fpdfsdk/javascript/cjs_runtime.cpp b/fpdfsdk/javascript/cjs_runtime.cpp
index a6da9c4..cb8f69f 100644
--- a/fpdfsdk/javascript/cjs_runtime.cpp
+++ b/fpdfsdk/javascript/cjs_runtime.cpp
@@ -147,8 +147,7 @@
 }
 
 IJS_EventContext* CJS_Runtime::NewEventContext() {
-  m_EventContextArray.push_back(
-      std::unique_ptr<CJS_EventContext>(new CJS_EventContext(this)));
+  m_EventContextArray.push_back(pdfium::MakeUnique<CJS_EventContext>(this));
   return m_EventContextArray.back().get();
 }