Update `bPrinting` in RenderPageImpl()

In RenderPageImpl(), if the embedder is trying to render a PDF to be
displayed as the preview of the printing result, the rendering flags
will contain FPDF_PRINTING and the device type is kDisplay.

To make sure that such print preview matches the actual printing
result, `bPrinting` should not only depend on device type, but also be
set to true as long as (flags & FPDF_PRINTING) is true.

Bug: pdfium:1658
Change-Id: I49fb8e0527e609c842f55e49c11e05f649de0c65
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/109310
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Nigi <nigi@chromium.org>
diff --git a/fpdfsdk/cpdfsdk_renderpage.cpp b/fpdfsdk/cpdfsdk_renderpage.cpp
index 9ffd683..757aa1f 100644
--- a/fpdfsdk/cpdfsdk_renderpage.cpp
+++ b/fpdfsdk/cpdfsdk_renderpage.cpp
@@ -69,6 +69,7 @@
     CPDF_AnnotList* pList = pOwnedList.get();
     pContext->m_pAnnots = std::move(pOwnedList);
     bool bPrinting =
+        (flags & FPDF_PRINTING) ||
         pContext->m_pDevice->GetDeviceType() != DeviceType::kDisplay;
 
     // TODO(https://crbug.com/pdfium/993) - maybe pass true here.