Bug 1821303 - Add hasPostData bool to nsISHEntry r=smaug

To avoid unnecessary cloning of nsIInputStream, add a hasPostData
boolean attribute to tell whether a nsISHEntry has populated postData.

Differential Revision: https://phabricator.services.mozilla.com/D173237

docshell/shistory/SessionHistoryEntry.cpp

@@ -715,6 +715,12 @@ SessionHistoryEntry::SetPostData(nsIInputStream* aPostData) {
   return NS_OK;
 }
 
+NS_IMETHODIMP
+SessionHistoryEntry::GetHasPostData(bool* aResult) {
+  *aResult = mInfo->HasPostData();
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 SessionHistoryEntry::GetLayoutHistoryState(
     nsILayoutHistoryState** aLayoutHistoryState) {

docshell/shistory/nsISHEntry.idl

@@ -128,6 +128,7 @@ interface nsISHEntry : nsISupports
 
     /** Post Data for the document */
     [infallible] attribute nsIInputStream postData;
+    [infallible] readonly attribute boolean hasPostData;
 
     /** LayoutHistoryState for scroll position and form values */
     [infallible] attribute nsILayoutHistoryState layoutHistoryState;

docshell/shistory/nsSHEntry.cpp

@@ -244,6 +244,12 @@ nsSHEntry::SetPostData(nsIInputStream* aPostData) {
   return NS_OK;
 }
 
+NS_IMETHODIMP
+nsSHEntry::GetHasPostData(bool* aResult) {
+  *aResult = !!mPostData;
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsSHEntry::GetLayoutHistoryState(nsILayoutHistoryState** aResult) {
   *aResult = mShared->mLayoutHistoryState;

toolkit/components/extensions/ExtensionDNR.sys.mjs

@@ -1368,7 +1368,7 @@ class RequestDetails {
         // See the above comment for more info.
         initiatorURI: parentPrin?.isContentPrincipal ? parentPrin.URI : null,
         type: isTop ? "main_frame" : "sub_frame",
-        method: bc.activeSessionHistoryEntry?.postData ? "post" : "get",
+        method: bc.activeSessionHistoryEntry?.hasPostData ? "post" : "get",
         tabId: this.tabId,
         // In this loop we are already explicitly accounting for ancestors, so
         // we intentionally omit browsingContext even though we have |bc|. If