CPDF_PageObjectHolder::GetDirtyStreams() returns const ref.

This is safer since a ref cannot be deleted.

Change-Id: Ib8d76ae2adb7c59e6955881eee0d2bd4db448b68
Reviewed-on: https://pdfium-review.googlesource.com/35950
Reviewed-by: Ryan Harrison <rharrison@chromium.org>
Commit-Queue: Henrique Nakashima <hnakashima@chromium.org>
diff --git a/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp b/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
index da6c74e..ba31516 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
+++ b/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
@@ -85,10 +85,10 @@
     if (pPageObj->IsDirty())
       all_dirty_streams.insert(pPageObj->GetContentStream());
   }
-  const std::set<int32_t>* marked_dirty_streams =
+  const std::set<int32_t>& marked_dirty_streams =
       m_pObjHolder->GetDirtyStreams();
-  all_dirty_streams.insert(marked_dirty_streams->begin(),
-                           marked_dirty_streams->end());
+  all_dirty_streams.insert(marked_dirty_streams.begin(),
+                           marked_dirty_streams.end());
 
   // Start regenerating dirty streams.
   std::map<int32_t, std::unique_ptr<std::ostringstream>> streams;
diff --git a/core/fpdfapi/edit/cpdf_pagecontentmanager.cpp b/core/fpdfapi/edit/cpdf_pagecontentmanager.cpp
index 46033bc..3ba23a8 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentmanager.cpp
+++ b/core/fpdfapi/edit/cpdf_pagecontentmanager.cpp
@@ -101,7 +101,7 @@
   // updated.
   // Since this is only called by CPDF_PageContentGenerator::GenerateContent(),
   // which cleans up the dirty streams first, this should always be true.
-  ASSERT(obj_holder_->GetDirtyStreams()->empty());
+  ASSERT(obj_holder_->GetDirtyStreams().empty());
 
   if (contents_stream_) {
     // Only stream that can be removed is 0.
diff --git a/core/fpdfapi/page/cpdf_pageobjectholder.h b/core/fpdfapi/page/cpdf_pageobjectholder.h
index d18f400..b1f7fb9 100644
--- a/core/fpdfapi/page/cpdf_pageobjectholder.h
+++ b/core/fpdfapi/page/cpdf_pageobjectholder.h
@@ -85,7 +85,7 @@
   void AddImageMaskBoundingBox(const CFX_FloatRect& box);
   void Transform(const CFX_Matrix& matrix);
   CFX_FloatRect CalcBoundingBox() const;
-  const std::set<int32_t>* GetDirtyStreams() const { return &m_DirtyStreams; }
+  const std::set<int32_t>& GetDirtyStreams() const { return m_DirtyStreams; }
   void ClearDirtyStreams() { m_DirtyStreams.clear(); }
 
   UnownedPtr<CPDF_Dictionary> m_pPageResources;