Bug 865729 - Use sXPConnect directly in caps. r=gabor

It's tempting to go through nsContentUtils here, but I'm pretty sure caps is
initialized before nsContentUtils.

caps/include/nsScriptSecurityManager.h

@@ -16,7 +16,6 @@
 #include "nsHashtable.h"
 #include "nsCOMPtr.h"
 #include "nsIChannelEventSink.h"
-#include "nsIJSContextStack.h"
 #include "nsIObserver.h"
 #include "pldhash.h"
 #include "plstr.h"
@@ -523,7 +522,6 @@ private:
 
     static nsIIOService    *sIOService;
     static nsIXPConnect    *sXPConnect;
-    static nsIThreadJSContextStack* sJSContextStack;
     static nsIStringBundle *sStrBundle;
     static JSRuntime       *sRuntime;
 };

caps/src/nsScriptSecurityManager.cpp

@@ -22,7 +22,6 @@
 #include "nsXPIDLString.h"
 #include "nsCRT.h"
 #include "nsCRTGlue.h"
-#include "nsIJSContextStack.h"
 #include "nsError.h"
 #include "nsDOMCID.h"
 #include "jsdbgapi.h"
@@ -73,7 +72,6 @@ static NS_DEFINE_CID(kZipReaderCID, NS_ZIPREADER_CID);
 
 nsIIOService    *nsScriptSecurityManager::sIOService = nullptr;
 nsIXPConnect    *nsScriptSecurityManager::sXPConnect = nullptr;
-nsIThreadJSContextStack *nsScriptSecurityManager::sJSContextStack = nullptr;
 nsIStringBundle *nsScriptSecurityManager::sStrBundle = nullptr;
 JSRuntime       *nsScriptSecurityManager::sRuntime   = 0;
 bool nsScriptSecurityManager::sStrictFileOriginPolicy = true;
@@ -265,7 +263,7 @@ nsScriptSecurityManager::GetCurrentJSContext()
 {
     // Get JSContext from stack.
     JSContext *cx;
-    if (NS_FAILED(sJSContextStack->Peek(&cx)))
+    if (NS_FAILED(sXPConnect->Peek(&cx)))
         return nullptr;
     return cx;
 }
@@ -274,7 +272,7 @@ JSContext *
 nsScriptSecurityManager::GetSafeJSContext()
 {
     // Get JSContext from stack.
-    return sJSContextStack->GetSafeJSContext();
+    return sXPConnect->GetSafeJSContext();
 }
 
 /* static */
@@ -2423,7 +2421,6 @@ nsresult nsScriptSecurityManager::Init()
         return NS_ERROR_FAILURE;
 
     NS_ADDREF(sXPConnect = xpconnect);
-    NS_ADDREF(sJSContextStack = xpconnect);
 
     JSContext* cx = GetSafeJSContext();
     if (!cx) return NS_ERROR_FAILURE;   // this can happen of xpt loading fails
@@ -2500,7 +2497,6 @@ nsScriptSecurityManager::Shutdown()
 
     NS_IF_RELEASE(sIOService);
     NS_IF_RELEASE(sXPConnect);
-    NS_IF_RELEASE(sJSContextStack);
     NS_IF_RELEASE(sStrBundle);
 }