Fix a Wrange-loop-analysis warnings in pdfium.

Bug: chromium:1039697
Change-Id: Ie0329ef20f24f18523ba7d9e23eaa0ebaf4d85bc
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/66891
Auto-Submit: Nico Weber <thakis@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>

core/fpdfapi/page/cpdf_contentmarks.cpp

diff --git a/core/fpdfapi/page/cpdf_contentmarks.cpp b/core/fpdfapi/page/cpdf_contentmarks.cpp
index 0b95ac5..9884152 100644
--- a/core/fpdfapi/page/cpdf_contentmarks.cpp
+++ b/core/fpdfapi/page/cpdf_contentmarks.cpp
@@ -109,7 +109,7 @@
 
 bool CPDF_ContentMarks::MarkData::ContainsItem(
     const CPDF_ContentMarkItem* pItem) const {
-  for (const auto pMark : m_Marks) {
+  for (const auto& pMark : m_Marks) {
     if (pMark == pItem)
       return true;
   }
@@ -126,7 +126,7 @@
 }
 
 int CPDF_ContentMarks::MarkData::GetMarkedContentID() const {
-  for (const auto pMark : m_Marks) {
+  for (const auto& pMark : m_Marks) {
     const CPDF_Dictionary* pDict = pMark->GetParam();
     if (pDict && pDict->KeyExist("MCID"))
       return pDict->GetIntegerFor("MCID");