Bug 1546736 Part 1 - Keep track of whether docshells and workers are being watched by the devtools, r=bzbarsky.

--HG--
extra : rebase_source : 837fc73223c0e275fce716bbe1108a14d0e9afa4

docshell/base/nsDocShell.cpp

@@ -386,7 +386,8 @@ nsDocShell::nsDocShell(BrowsingContext* aBrowsingContext)
       mBlankTiming(false),
       mTitleValidForCurrentURI(false),
       mIsFrame(false),
-      mSkipBrowsingContextDetachOnDestroy(false) {
+      mSkipBrowsingContextDetachOnDestroy(false),
+      mWatchedByDevtools(false) {
   mHistoryID.m0 = 0;
   mHistoryID.m1 = 0;
   mHistoryID.m2 = 0;
@@ -13548,3 +13549,16 @@ bool nsDocShell::GetIsAttemptingToNavigate() {
 
   return false;
 }
+
+NS_IMETHODIMP
+nsDocShell::GetWatchedByDevtools(bool* aWatched) {
+  NS_ENSURE_ARG(aWatched);
+  *aWatched = mWatchedByDevtools;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDocShell::SetWatchedByDevtools(bool aWatched) {
+  mWatchedByDevtools = aWatched;
+  return NS_OK;
+}

docshell/base/nsDocShell.h

@@ -1245,6 +1245,9 @@ class nsDocShell final : public nsDocLoader,
   // docshell is destroyed, the browsing context will not be detached. This is
   // for cases where we want to preserve the BC for future use.
   bool mSkipBrowsingContextDetachOnDestroy : 1;
+
+  // Set when activity in this docshell is being watched by the developer tools.
+  bool mWatchedByDevtools : 1;
 };
 
 #endif /* nsDocShell_h__ */

docshell/base/nsIDocShell.idl

@@ -1167,4 +1167,9 @@ interface nsIDocShell : nsIDocShellTreeItem
    * sense that's relevant to document.open.
    */
   [notxpcom, nostdcall] readonly attribute boolean isAttemptingToNavigate;
+
+  /**
+   * Whether developer tools are watching activity in this docshell.
+   */
+  [infallible] attribute boolean watchedByDevtools;
 };

dom/base/SerializedStackHolder.h

@@ -49,10 +49,9 @@ class SerializedStackHolder {
 // monitor later on. This may be called on either the main or a worker thread.
 //
 // This always creates a stack, even if the net monitor isn't active for the
-// associated window. Ideally we would only create the stack if the net monitor
-// was active, but there doesn't seem to be an easy way to determine this.
-// The operations this is used with should be rare enough and/or have enough
-// other associated costs that the perf impact is low. See bug 1546736.
+// associated window. The net monitor will only be active if the associated
+// docshell or worker's WatchedByDevtools flag is set, so this should be checked
+// before creating the stack.
 UniquePtr<SerializedStackHolder> GetCurrentStackForNetMonitor(JSContext* aCx);
 
 // If aStackHolder is non-null, this notifies the net monitor that aStackHolder

dom/workers/WorkerLoadInfo.cpp

@@ -87,6 +87,7 @@ WorkerLoadInfoData::WorkerLoadInfoData()
       mReportCSPViolations(false),
       mXHRParamsAllowed(false),
       mPrincipalIsSystem(false),
+      mWatchedByDevtools(false),
       mStorageAccess(nsContentUtils::StorageAccess::eDeny),
       mFirstPartyStorageAccessGranted(false),
       mServiceWorkersTestingInWindow(false),

dom/workers/WorkerLoadInfo.h

@@ -118,6 +118,7 @@ struct WorkerLoadInfoData {
   bool mReportCSPViolations;
   bool mXHRParamsAllowed;
   bool mPrincipalIsSystem;
+  bool mWatchedByDevtools;
   nsContentUtils::StorageAccess mStorageAccess;
   bool mFirstPartyStorageAccessGranted;
   bool mServiceWorkersTestingInWindow;

dom/workers/WorkerPrivate.cpp

@@ -2366,6 +2366,7 @@ nsresult WorkerPrivate::GetLoadInfo(JSContext* aCx, nsPIDOMWindowInner* aWindow,
     loadInfo.mServiceWorkersTestingInWindow =
         aParent->ServiceWorkersTestingInWindow();
     loadInfo.mParentController = aParent->GetController();
+    loadInfo.mWatchedByDevtools = aParent->IsWatchedByDevtools();
   } else {
     AssertIsOnMainThread();
 
@@ -2486,6 +2487,11 @@ nsresult WorkerPrivate::GetLoadInfo(JSContext* aCx, nsPIDOMWindowInner* aWindow,
 
       loadInfo.mXHRParamsAllowed = perm == nsIPermissionManager::ALLOW_ACTION;
 
+      nsIDocShell* docShell = globalWindow->GetDocShell();
+      if (docShell) {
+        loadInfo.mWatchedByDevtools = docShell->GetWatchedByDevtools();
+      }
+
       loadInfo.mFromWindow = true;
       loadInfo.mWindowID = globalWindow->WindowID();
       loadInfo.mStorageAccess =

dom/workers/WorkerPrivate.h

@@ -768,6 +768,10 @@ class WorkerPrivate : public RelativeTimeline {
     return mLoadInfo.mServiceWorkersTestingInWindow;
   }
 
+  bool IsWatchedByDevtools() const {
+    return mLoadInfo.mWatchedByDevtools;
+  }
+
   // Determine if the worker is currently loading its top level script.
   bool IsLoadingWorkerScript() const { return mLoadingWorkerScript; }