Add CPDF_Array::IsEmpty().

Using IsEmpty() is more readable than using GetCount() == 0.

Review-Url: https://codereview.chromium.org/2226113002
diff --git a/core/fpdfapi/fpdf_page/cpdf_colorspace.cpp b/core/fpdfapi/fpdf_page/cpdf_colorspace.cpp
index 9d3aeb2..759d0f3 100644
--- a/core/fpdfapi/fpdf_page/cpdf_colorspace.cpp
+++ b/core/fpdfapi/fpdf_page/cpdf_colorspace.cpp
@@ -355,7 +355,7 @@
   }
 
   CPDF_Array* pArray = pObj->AsArray();
-  if (!pArray || pArray->GetCount() == 0)
+  if (!pArray || pArray->IsEmpty())
     return nullptr;
 
   CPDF_Object* pFamilyObj = pArray->GetDirectObjectAt(0);
diff --git a/core/fpdfapi/fpdf_page/fpdf_page_doc.cpp b/core/fpdfapi/fpdf_page/fpdf_page_doc.cpp
index 059679a..f8d7575 100644
--- a/core/fpdfapi/fpdf_page/fpdf_page_doc.cpp
+++ b/core/fpdfapi/fpdf_page/fpdf_page_doc.cpp
@@ -275,7 +275,7 @@
   }
 
   CPDF_Array* pArray = pCSObj->AsArray();
-  if (!pArray || pArray->GetCount() == 0)
+  if (!pArray || pArray->IsEmpty())
     return nullptr;
 
   if (pArray->GetCount() == 1) {
diff --git a/core/fpdfapi/fpdf_parser/include/cpdf_array.h b/core/fpdfapi/fpdf_parser/include/cpdf_array.h
index 0629046..9bb99da 100644
--- a/core/fpdfapi/fpdf_parser/include/cpdf_array.h
+++ b/core/fpdfapi/fpdf_parser/include/cpdf_array.h
@@ -28,6 +28,7 @@
   CPDF_Array* AsArray() override;
   const CPDF_Array* AsArray() const override;
 
+  bool IsEmpty() const { return m_Objects.empty(); }
   size_t GetCount() const { return m_Objects.size(); }
   CPDF_Object* GetObjectAt(size_t index) const;
   CPDF_Object* GetDirectObjectAt(size_t index) const;
diff --git a/core/fpdfdoc/cpdf_formfield.cpp b/core/fpdfdoc/cpdf_formfield.cpp
index 81d2178..ac6c01b 100644
--- a/core/fpdfdoc/cpdf_formfield.cpp
+++ b/core/fpdfdoc/cpdf_formfield.cpp
@@ -887,7 +887,7 @@
     if (bSelected)
       pArray->AddInteger(iOptIndex);
 
-    if (pArray->GetCount() == 0)
+    if (pArray->IsEmpty())
       m_pDict->RemoveAt("I");
   }
   if (bNotify)