Revert "Revert "Use UnownedPtr instead of T* in MaybeOwned.""

This reverts commit 77d8ed02c7e97471ceccee5abbabeb2fdea413c7.

Reason for revert: <INSERT REASONING HERE>

Original change's description:
> Revert "Use UnownedPtr instead of T* in MaybeOwned."
> 
> This reverts commit e563e8352139e4852a955e319023b09f2844aee9.
> 
> Reason for revert: <INSERT REASONING HERE>
> 
> Original change's description:
> > Use UnownedPtr instead of T* in MaybeOwned.
> > 
> > Always check the liftime in the unowned case. Doing so unearthed
> > the following issues:
> > 
> > Transient lifetime issue in jbig2_image when doing realloc().
> > Stale (but unused) dictionary pointer in CPDF_Image.
> > Destruction order in error branch in cpdf_dibsource.cpp
> > 
> > Change-Id: I12b758aafeefedc7abe1e8b21a18db959929e95f
> > Reviewed-on: https://pdfium-review.googlesource.com/24552
> > Commit-Queue: Tom Sepez <tsepez@chromium.org>
> > Reviewed-by: dsinclair <dsinclair@chromium.org>
> 
> TBR=thestig@chromium.org,tsepez@chromium.org,dsinclair@chromium.org
> 
> Change-Id: I3c56ee6ab502da90e3adb7507dbc8cc92f090140
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://pdfium-review.googlesource.com/24670
> Reviewed-by: Tom Sepez <tsepez@chromium.org>
> Commit-Queue: Tom Sepez <tsepez@chromium.org>

TBR=thestig@chromium.org,tsepez@chromium.org,dsinclair@chromium.org

Change-Id: I0ccbbeab8be6cadc9b3a5bfefe2aca733654342f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://pdfium-review.googlesource.com/24671
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

core/fpdfapi/page/cpdf_image.cpp

diff --git a/core/fpdfapi/page/cpdf_image.cpp b/core/fpdfapi/page/cpdf_image.cpp
index 65ca78e..5f82886 100644
--- a/core/fpdfapi/page/cpdf_image.cpp
+++ b/core/fpdfapi/page/cpdf_image.cpp
@@ -35,33 +35,27 @@
 
 CPDF_Image::CPDF_Image(CPDF_Document* pDoc,
                        std::unique_ptr<CPDF_Stream> pStream)
-    : m_bIsInline(true),
-      m_pDocument(pDoc),
-      m_pStream(std::move(pStream)),
-      m_pDict(ToDictionary(m_pStream->GetDict()->Clone())) {
+    : m_bIsInline(true), m_pDocument(pDoc), m_pStream(std::move(pStream)) {
   ASSERT(m_pStream.IsOwned());
-  ASSERT(m_pDict.IsOwned());
-  FinishInitialization();
+  FinishInitialization(m_pStream->GetDict());
 }
 
 CPDF_Image::CPDF_Image(CPDF_Document* pDoc, uint32_t dwStreamObjNum)
     : m_pDocument(pDoc),
-      m_pStream(ToStream(pDoc->GetIndirectObject(dwStreamObjNum))),
-      m_pDict(m_pStream->GetDict()) {
+      m_pStream(ToStream(pDoc->GetIndirectObject(dwStreamObjNum))) {
   ASSERT(!m_pStream.IsOwned());
-  ASSERT(!m_pDict.IsOwned());
-  FinishInitialization();
+  FinishInitialization(m_pStream->GetDict());
 }
 
 CPDF_Image::~CPDF_Image() {}
 
-void CPDF_Image::FinishInitialization() {
-  m_pOC = m_pDict->GetDictFor("OC");
+void CPDF_Image::FinishInitialization(CPDF_Dictionary* pDict) {
+  m_pOC = pDict->GetDictFor("OC");
   m_bIsMask =
-      !m_pDict->KeyExist("ColorSpace") || m_pDict->GetIntegerFor("ImageMask");
-  m_bInterpolate = !!m_pDict->GetIntegerFor("Interpolate");
-  m_Height = m_pDict->GetIntegerFor("Height");
-  m_Width = m_pDict->GetIntegerFor("Width");
+      !pDict->KeyExist("ColorSpace") || pDict->GetIntegerFor("ImageMask");
+  m_bInterpolate = !!pDict->GetIntegerFor("Interpolate");
+  m_Height = pDict->GetIntegerFor("Height");
+  m_Width = pDict->GetIntegerFor("Width");
 }
 
 void CPDF_Image::ConvertStreamToIndirectObject() {