Add CPDF_Dictionary::GetNumberFor() helper method

Introduce this method now that name conflicts are resolved.

Change-Id: I05cbfa9e6f258fd4120f0da654e605cea5565ec1
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/97771
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

core/fpdfapi/page/cpdf_expintfunc.cpp

diff --git a/core/fpdfapi/page/cpdf_expintfunc.cpp b/core/fpdfapi/page/cpdf_expintfunc.cpp
index 9fa9fb3..cde595f 100644
--- a/core/fpdfapi/page/cpdf_expintfunc.cpp
+++ b/core/fpdfapi/page/cpdf_expintfunc.cpp
@@ -25,7 +25,7 @@
   if (!pDict)
     return false;
 
-  const CPDF_Number* pExponent = ToNumber(pDict->GetObjectFor("N"));
+  RetainPtr<const CPDF_Number> pExponent = pDict->GetNumberFor("N");
   if (!pExponent)
     return false;
 

core/fpdfapi/parser/cpdf_dictionary.cpp

diff --git a/core/fpdfapi/parser/cpdf_dictionary.cpp b/core/fpdfapi/parser/cpdf_dictionary.cpp
index 7504cb6..27c4c13 100644
--- a/core/fpdfapi/parser/cpdf_dictionary.cpp
+++ b/core/fpdfapi/parser/cpdf_dictionary.cpp
@@ -202,6 +202,11 @@
   return pdfium::WrapRetain(const_cast<CPDF_Stream*>(GetStreamFor(key)));
 }
 
+RetainPtr<const CPDF_Number> CPDF_Dictionary::GetNumberFor(
+    const ByteString& key) const {
+  return pdfium::WrapRetain(ToNumber(GetObjectFor(key)));
+}
+
 CFX_FloatRect CPDF_Dictionary::GetRectFor(const ByteString& key) const {
   CFX_FloatRect rect;
   const CPDF_Array* pArray = GetArrayFor(key);

core/fpdfapi/parser/cpdf_dictionary.h

diff --git a/core/fpdfapi/parser/cpdf_dictionary.h b/core/fpdfapi/parser/cpdf_dictionary.h
index c8d2a6e..5837121 100644
--- a/core/fpdfapi/parser/cpdf_dictionary.h
+++ b/core/fpdfapi/parser/cpdf_dictionary.h
@@ -74,6 +74,7 @@
   RetainPtr<CPDF_Array> GetOrCreateArrayFor(const ByteString& key);
   const CPDF_Stream* GetStreamFor(const ByteString& key) const;
   RetainPtr<CPDF_Stream> GetMutableStreamFor(const ByteString& key);
+  RetainPtr<const CPDF_Number> GetNumberFor(const ByteString& key) const;
   CFX_FloatRect GetRectFor(const ByteString& key) const;
   CFX_Matrix GetMatrixFor(const ByteString& key) const;
 

core/fpdfapi/parser/cpdf_linearized_header.cpp

diff --git a/core/fpdfapi/parser/cpdf_linearized_header.cpp b/core/fpdfapi/parser/cpdf_linearized_header.cpp
index 4871739..adedf3b 100644
--- a/core/fpdfapi/parser/cpdf_linearized_header.cpp
+++ b/core/fpdfapi/parser/cpdf_linearized_header.cpp
@@ -31,7 +31,7 @@
                                    bool must_exist = true) {
   if (!pDict->KeyExist(key))
     return !must_exist;
-  const CPDF_Number* pNum = ToNumber(pDict->GetObjectFor(key));
+  RetainPtr<const CPDF_Number> pNum = pDict->GetNumberFor(key);
   if (!pNum || !pNum->IsInteger())
     return false;
   const int raw_value = pNum->GetInteger();

core/fpdfapi/parser/cpdf_object_stream.cpp

diff --git a/core/fpdfapi/parser/cpdf_object_stream.cpp b/core/fpdfapi/parser/cpdf_object_stream.cpp
index 93bd12b..3a55e4f 100644
--- a/core/fpdfapi/parser/cpdf_object_stream.cpp
+++ b/core/fpdfapi/parser/cpdf_object_stream.cpp
@@ -31,8 +31,8 @@
   if (!ValidateDictType(stream_dict, "ObjStm"))
     return false;
 
-  const CPDF_Number* number_of_objects =
-      ToNumber(stream_dict->GetObjectFor("N"));
+  RetainPtr<const CPDF_Number> number_of_objects =
+      stream_dict->GetNumberFor("N");
   if (!number_of_objects || !number_of_objects->IsInteger() ||
       number_of_objects->GetInteger() < 0 ||
       number_of_objects->GetInteger() >=
@@ -40,8 +40,8 @@
     return false;
   }
 
-  const CPDF_Number* first_object_offset =
-      ToNumber(stream_dict->GetObjectFor("First"));
+  RetainPtr<const CPDF_Number> first_object_offset =
+      stream_dict->GetNumberFor("First");
   if (!first_object_offset || !first_object_offset->IsInteger() ||
       first_object_offset->GetInteger() < 0) {
     return false;