Apply pdfium_noshorten_config to fpdfsdk/

Convert remaining code to avoid unchecked shortening conversions.

-- rewrite a loop in GetPageIndexByAnnotDict()

Change-Id: I396a058525de0ff90e96a39e0cc28a937cc94484
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/91353
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
diff --git a/fpdfsdk/cpdfsdk_formfillenvironment.cpp b/fpdfsdk/cpdfsdk_formfillenvironment.cpp
index beed063..5f6aec8 100644
--- a/fpdfsdk/cpdfsdk_formfillenvironment.cpp
+++ b/fpdfsdk/cpdfsdk_formfillenvironment.cpp
@@ -408,7 +408,9 @@
     size_t nCharacters = text.GetLength();
     ByteString bsUTFText = text.ToUTF16LE();
     auto* pBuffer = reinterpret_cast<const unsigned short*>(bsUTFText.c_str());
-    m_pInfo->FFI_SetTextFieldFocus(m_pInfo, pBuffer, nCharacters, bFocus);
+    m_pInfo->FFI_SetTextFieldFocus(
+        m_pInfo, pBuffer, pdfium::base::checked_cast<FPDF_DWORD>(nCharacters),
+        bFocus);
   }
 }