Break linkage from CPDFXA_DocEnvironment to IJS_EventContext.

CPDFXFA_DocEnvionment is part of the heirarchy of objects owned by
the embedder under its FPDF_Document object.

IJS_EventContext is part of the hierarchy of objects owned by the
embedder under its FPDF_FormHandle object.

The FPDF_Document must outlive the FPDF_FormHandle, so there is a
lifetime inversion with the m_pJSEventContext member.  No matter,
event contexts are transient and allocated in a stack-based manner
as control bounces from C++ to JS and vice versa, and keeping a
persistent one seems wrong.  So make it only as needed.

Bug: 723644
Change-Id: I74dd328ad4b501e4adf57821b44ecc78d945eb0f
Reviewed-on: https://pdfium-review.googlesource.com/5656
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>

2 files changed, 14 insertions, 19 deletions

diff --git a/fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.cpp b/fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.cpp
index 11b001fc7f..4695c64ce1 100644
--- a/fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.cpp
+++ b/fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.cpp
@@ -39,16 +39,11 @@
 #define FXFA_XFA_ALL 0x01111111
 
 CPDFXFA_DocEnvironment::CPDFXFA_DocEnvironment(CPDFXFA_Context* pContext)
-    : m_pContext(pContext), m_pJSEventContext(nullptr) {
+    : m_pContext(pContext) {
   ASSERT(m_pContext);
 }
 
-CPDFXFA_DocEnvironment::~CPDFXFA_DocEnvironment() {
-  if (m_pJSEventContext && m_pContext->GetFormFillEnv()) {
-    m_pContext->GetFormFillEnv()->GetJSRuntime()->ReleaseEventContext(
-        m_pJSEventContext.Get());
-  }
-}
+CPDFXFA_DocEnvironment::~CPDFXFA_DocEnvironment() {}
 
 void CPDFXFA_DocEnvironment::SetChangeMark(CXFA_FFDoc* hDoc) {
   if (hDoc == m_pContext->GetXFADoc() && m_pContext->GetFormFillEnv())
@@ -1006,13 +1001,15 @@ bool CPDFXFA_DocEnvironment::SetGlobalProperty(
     CFXJSE_Value* pValue) {
   if (hDoc != m_pContext->GetXFADoc())
     return false;
-
-  if (m_pContext->GetFormFillEnv() &&
-      m_pContext->GetFormFillEnv()->GetJSRuntime()) {
-    return m_pContext->GetFormFillEnv()->GetJSRuntime()->SetValueByName(
-        szPropName, pValue);
+  if (!m_pContext->GetFormFillEnv() ||
+      !m_pContext->GetFormFillEnv()->GetJSRuntime()) {
+    return false;
   }
-  return false;
+  CPDFSDK_FormFillEnvironment* pFormFillEnv = m_pContext->GetFormFillEnv();
+  IJS_EventContext* pContext = pFormFillEnv->GetJSRuntime()->NewEventContext();
+  bool bRet = pFormFillEnv->GetJSRuntime()->SetValueByName(szPropName, pValue);
+  pFormFillEnv->GetJSRuntime()->ReleaseEventContext(pContext);
+  return bRet;
 }
 
 bool CPDFXFA_DocEnvironment::GetGlobalProperty(
@@ -1025,10 +1022,9 @@ bool CPDFXFA_DocEnvironment::GetGlobalProperty(
       !m_pContext->GetFormFillEnv()->GetJSRuntime()) {
     return false;
   }
-
   CPDFSDK_FormFillEnvironment* pFormFillEnv = m_pContext->GetFormFillEnv();
-  if (!m_pJSEventContext)
-    m_pJSEventContext = pFormFillEnv->GetJSRuntime()->NewEventContext();
-
-  return pFormFillEnv->GetJSRuntime()->GetValueByName(szPropName, pValue);
+  IJS_EventContext* pContext = pFormFillEnv->GetJSRuntime()->NewEventContext();
+  bool bRet = pFormFillEnv->GetJSRuntime()->GetValueByName(szPropName, pValue);
+  pFormFillEnv->GetJSRuntime()->ReleaseEventContext(pContext);
+  return bRet;
 }
diff --git a/fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.h b/fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.h
index ec04e78db9..90bc6dea04 100644
--- a/fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.h
+++ b/fpdfsdk/fpdfxfa/cpdfxfa_docenvironment.h
@@ -107,7 +107,6 @@ class CPDFXFA_DocEnvironment : public IXFA_DocEnvironment {
   void ToXFAContentFlags(CFX_WideString csSrcContent, FPDF_DWORD& flag);
 
   CFX_UnownedPtr<CPDFXFA_Context> const m_pContext;
-  CFX_UnownedPtr<IJS_EventContext> m_pJSEventContext;
 };
 
 #endif  // FPDFSDK_FPDFXFA_CPDFXFA_DOCENVIRONMENT_H_