Fix issue when firing TimerProc() destroys timer

fpdfsdk/javascript/JS_Object.cpp

Index: fpdfsdk/javascript/JS_Object.cpp
diff --git a/fpdfsdk/javascript/JS_Object.cpp b/fpdfsdk/javascript/JS_Object.cpp
index b0a307beb11a368849c6fcdfeca548fc38ec9ea3..bef996505555da5c4c0ff3d20fba8a0d5ed0edcc 100644
--- a/fpdfsdk/javascript/JS_Object.cpp
+++ b/fpdfsdk/javascript/JS_Object.cpp
@@ -115,16 +115,24 @@ void CJS_Timer::KillJSTimer() {
 
 // static
 void CJS_Timer::TimerProc(int idEvent) {
-  const auto it = GetGlobalTimerMap()->find(idEvent);
-  if (it != GetGlobalTimerMap()->end()) {
-    CJS_Timer* pTimer = it->second;
-    if (!pTimer->m_bProcessing) {
-      CFX_AutoRestorer<bool> scoped_processing(&pTimer->m_bProcessing);
-      pTimer->m_bProcessing = true;
-      if (pTimer->m_pEmbedObj)
-        pTimer->m_pEmbedObj->TimerProc(pTimer);
-    }
-  }
+  auto it = GetGlobalTimerMap()->find(idEvent);
+  if (it == GetGlobalTimerMap()->end())
+    return;
+
+  CJS_Timer* pTimer = it->second;
+  if (pTimer->m_bProcessing)
+    return;
+
+  pTimer->m_bProcessing = true;
+  if (pTimer->m_pEmbedObj)
+    pTimer->m_pEmbedObj->TimerProc(pTimer);
+
+  // Timer proc may have destroyed timer, find it again.

[Lei Zhang, 2016/08/04 19:02:40]

Is it possible for a new timer with the same |idEvent| to get set from running
the timer proc, thus destroying |pTimer|, but putting a new timer into the same
slot in the map?

[Tom Sepez, 2016/08/04 19:12:40]

It's up to the embedder, and doesn't happen AFAICT with our various embedders,
but doesn't hurt to check.  Other things probably go off the rails if they are
reused ...

+  it = GetGlobalTimerMap()->find(idEvent);
+  if (it == GetGlobalTimerMap()->end())
+    return;
+
+  pTimer->m_bProcessing = false;
 }
 
 // static