Allow creation of a MaybeOwned<T> from UnownedPtr<T>.

Small test to show these forms compile and do not transfer ownership.

Change-Id: I1787a57d4d0bf70da7b6101c1f958cfe9a8f9dda
Reviewed-on: https://pdfium-review.googlesource.com/40830
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

2 files changed, 21 insertions, 0 deletions

diff --git a/core/fxcrt/maybe_owned.h b/core/fxcrt/maybe_owned.h
index d920ea7a91..ac3a81d47e 100644
--- a/core/fxcrt/maybe_owned.h
+++ b/core/fxcrt/maybe_owned.h
@@ -24,6 +24,7 @@ class MaybeOwned {
  public:
   MaybeOwned() : m_pObj(nullptr) {}
   explicit MaybeOwned(T* ptr) : m_pObj(ptr) {}
+  explicit MaybeOwned(const UnownedPtr<T>& ptr) : m_pObj(ptr.Get()) {}
   explicit MaybeOwned(std::unique_ptr<T, D> ptr)
       : m_pOwnedObj(std::move(ptr)), m_pObj(m_pOwnedObj.get()) {}
 
@@ -74,6 +75,10 @@ class MaybeOwned {
     Reset(ptr);
     return *this;
   }
+  MaybeOwned& operator=(const UnownedPtr<T>& ptr) {
+    Reset(ptr.Get());
+    return *this;
+  }
   MaybeOwned& operator=(std::unique_ptr<T, D> ptr) {
     Reset(std::move(ptr));
     return *this;
diff --git a/core/fxcrt/maybe_owned_unittest.cpp b/core/fxcrt/maybe_owned_unittest.cpp
index 7182647207..e1637c59b3 100644
--- a/core/fxcrt/maybe_owned_unittest.cpp
+++ b/core/fxcrt/maybe_owned_unittest.cpp
@@ -8,6 +8,7 @@
 #include <utility>
 
 #include "core/fxcrt/fx_memory.h"
+#include "core/fxcrt/unowned_ptr.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/base/ptr_util.h"
 
@@ -80,6 +81,21 @@ TEST(MaybeOwned, NotOwned) {
   EXPECT_EQ(1, owned_delete_count);
 }
 
+TEST(MaybeOwned, UnownedPtr) {
+  int delete_count = 0;
+  PseudoDeletable thing1(100, &delete_count);
+  PseudoDeletable thing2(200, &delete_count);
+  UnownedPtr<PseudoDeletable> unowned1(&thing1);
+  UnownedPtr<PseudoDeletable> unowned2(&thing2);
+  {
+    MaybeOwned<PseudoDeletable> ptr1(unowned1);
+    MaybeOwned<PseudoDeletable> ptr2(unowned2);
+    ptr2 = unowned1;
+    ptr1 = unowned2;
+  }
+  EXPECT_EQ(0, delete_count);
+}
+
 TEST(MaybeOwned, Owned) {
   int delete_count = 0;
   {