Make SharedCopyOnWrite use Retainables

This CL removes the CountedObject from SharedCopyOnWrite and instead
converts the items being shared into Retainable subclasses.

BUG: chromium:792372
Change-Id: I9570a521f2fc2434013c3ccb103273bdd2440bb8
Reviewed-on: https://pdfium-review.googlesource.com/22010
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>

2 files changed, 6 insertions, 31 deletions

diff --git a/core/fxcrt/shared_copy_on_write.h b/core/fxcrt/shared_copy_on_write.h
index c04730d5e0..f7d7a2afdb 100644
--- a/core/fxcrt/shared_copy_on_write.h
+++ b/core/fxcrt/shared_copy_on_write.h
@@ -24,7 +24,7 @@ class SharedCopyOnWrite {
 
   template <typename... Args>
   ObjClass* Emplace(Args... params) {
-    m_pObject.Reset(new CountedObj(params...));
+    m_pObject.Reset(new ObjClass(params...));
     return m_pObject.Get();
   }
 
@@ -42,7 +42,7 @@ class SharedCopyOnWrite {
     if (!m_pObject)
       return Emplace(params...);
     if (!m_pObject->HasOneRef())
-      m_pObject.Reset(new CountedObj(*m_pObject));
+      m_pObject.Reset(new ObjClass(*m_pObject));
     return m_pObject.Get();
   }
 
@@ -55,33 +55,7 @@ class SharedCopyOnWrite {
   explicit operator bool() const { return !!m_pObject; }
 
  private:
-  class CountedObj : public ObjClass {
-   public:
-    template <typename... Args>
-    // NOLINTNEXTLINE(runtime/explicit)
-    CountedObj(Args... params) : ObjClass(params...), m_RefCount(0) {}
-
-    CountedObj(const CountedObj& src) : ObjClass(src), m_RefCount(0) {}
-    ~CountedObj() { m_RefCount = 0; }
-
-    bool HasOneRef() const { return m_RefCount == 1; }
-    void Retain() { m_RefCount++; }
-    void Release() {
-      ASSERT(m_RefCount);
-      if (--m_RefCount == 0)
-        delete this;
-    }
-
-   private:
-    // To ensure ref counts do not overflow, consider the worst possible case:
-    // the entire address space contains nothing but pointers to this object.
-    // Since the count increments with each new pointer, the largest value is
-    // the number of pointers that can fit into the address space. The size of
-    // the address space itself is a good upper bound on it.
-    intptr_t m_RefCount;
-  };
-
-  RetainPtr<CountedObj> m_pObject;
+  RetainPtr<ObjClass> m_pObject;
 };
 
 }  // namespace fxcrt
diff --git a/core/fxcrt/shared_copy_on_write_unittest.cpp b/core/fxcrt/shared_copy_on_write_unittest.cpp
index 01cc09468c..57e33d1019 100644
--- a/core/fxcrt/shared_copy_on_write_unittest.cpp
+++ b/core/fxcrt/shared_copy_on_write_unittest.cpp
@@ -7,6 +7,7 @@
 #include <map>
 #include <string>
 
+#include "core/fxcrt/retain_ptr.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace fxcrt {
@@ -28,7 +29,7 @@ class Observer {
   std::map<std::string, int> destruction_counts_;
 };
 
-class Object {
+class Object : public Retainable {
  public:
   Object(Observer* observer, const std::string& name)
       : name_(name), observer_(observer) {
@@ -37,7 +38,7 @@ class Object {
   Object(const Object& that) : name_(that.name_), observer_(that.observer_) {
     observer_->OnConstruct(name_);
   }
-  ~Object() { observer_->OnDestruct(name_); }
+  ~Object() override { observer_->OnDestruct(name_); }
 
  private:
   std::string name_;