Pass const-ref to CPDF_PageContentGenerator::UpdateContentStreams()

Prefer const-ref over pointer for objects that are not mutated by
the callee. Found by overzealous grep while looking for pointers to
std::unique_ptr<>.

We can now avoid a local in the caller since we can just pass a rvalue
without having to apply & (address-of).

Change-Id: I7a0f6d38edee02f006c40434be4756d514135094
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/77090
Reviewed-by: Hui Yingst <nigi@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp

diff --git a/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp b/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
index f371ffa..0b298ab 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
+++ b/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
@@ -67,11 +67,7 @@
 
 void CPDF_PageContentGenerator::GenerateContent() {
   ASSERT(m_pObjHolder->IsPage());
-
-  std::map<int32_t, std::unique_ptr<std::ostringstream>> stream =
-      GenerateModifiedStreams();
-
-  UpdateContentStreams(&stream);
+  UpdateContentStreams(GenerateModifiedStreams());
 }
 
 std::map<int32_t, std::unique_ptr<std::ostringstream>>
@@ -144,14 +140,15 @@
 }
 
 void CPDF_PageContentGenerator::UpdateContentStreams(
-    std::map<int32_t, std::unique_ptr<std::ostringstream>>* new_stream_data) {
+    const std::map<int32_t, std::unique_ptr<std::ostringstream>>&
+        new_stream_data) {
   // If no streams were regenerated or removed, nothing to do here.
-  if (new_stream_data->empty())
+  if (new_stream_data.empty())
     return;
 
   CPDF_PageContentManager page_content_manager(m_pObjHolder.Get());
 
-  for (auto& pair : *new_stream_data) {
+  for (auto& pair : new_stream_data) {
     int32_t stream_index = pair.first;
     std::ostringstream* buf = pair.second.get();
 

core/fpdfapi/edit/cpdf_pagecontentgenerator.h

diff --git a/core/fpdfapi/edit/cpdf_pagecontentgenerator.h b/core/fpdfapi/edit/cpdf_pagecontentgenerator.h
index f1126f2..79bcdff 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentgenerator.h
+++ b/core/fpdfapi/edit/cpdf_pagecontentgenerator.h
@@ -60,7 +60,8 @@
 
   // Add buffer as a stream in page's 'Contents'
   void UpdateContentStreams(
-      std::map<int32_t, std::unique_ptr<std::ostringstream>>* new_stream_data);
+      const std::map<int32_t, std::unique_ptr<std::ostringstream>>&
+          new_stream_data);
 
   // Set the stream index of all page objects with stream index ==
   // |CPDF_PageObject::kNoContentStream|. These are new objects that had not