Make code compile with clang_use_chrome_plugin (part I)

core/fpdfapi/fpdf_page/cpdf_formobject.cpp

Index: core/fpdfapi/fpdf_page/cpdf_formobject.cpp
diff --git a/core/fpdfapi/fpdf_page/cpdf_formobject.cpp b/core/fpdfapi/fpdf_page/cpdf_formobject.cpp
index d85ff7dbb3ffc0e7d77724ee9ba0b14d299332ed..567c156af0af3bac076518bd4c9dcfd4a2b7aa79 100644
--- a/core/fpdfapi/fpdf_page/cpdf_formobject.cpp
+++ b/core/fpdfapi/fpdf_page/cpdf_formobject.cpp
@@ -19,6 +19,18 @@ void CPDF_FormObject::Transform(const CFX_Matrix& matrix) {
   CalcBoundingBox();
 }
 
+bool CPDF_FormObject::IsForm() const {
+  return true;
+}
+
+CPDF_FormObject* CPDF_FormObject::AsForm() {
+  return this;
+}
+
+const CPDF_FormObject* CPDF_FormObject::AsForm() const {
+  return this;
+}
+
 CPDF_FormObject* CPDF_FormObject::Clone() const {
   CPDF_FormObject* obj = new CPDF_FormObject;
   obj->CopyData(this);
@@ -28,6 +40,10 @@ CPDF_FormObject* CPDF_FormObject::Clone() const {
   return obj;
 }
 
+CPDF_PageObject::Type CPDF_FormObject::GetType() const {
+  return FORM;
+}
+
 void CPDF_FormObject::CalcBoundingBox() {
   CFX_FloatRect form_rect = m_pForm->CalcBoundingBox();
   form_rect.Transform(&m_FormMatrix);