Bug 1804295, Add GeckoTasksBurst, r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D165133

widget/nsBaseAppShell.cpp

@@ -26,10 +26,8 @@ nsBaseAppShell::nsBaseAppShell()
     : mSuspendNativeCount(0),
       mEventloopNestingLevel(0),
       mBlockedWait(nullptr),
-      mFavorPerf(0),
       mNativeEventPending(false),
-      mStarvationDelay(0),
-      mSwitchTime(0),
+      mGeckoTaskBurstStartTime(0),
       mLastNativeEventTime(0),
       mEventloopNestingState(eEventloopNone),
       mRunning(false),
@@ -165,14 +163,9 @@ nsBaseAppShell::Exit(void) {
 }
 
 NS_IMETHODIMP
-nsBaseAppShell::FavorPerformanceHint(bool favorPerfOverStarvation,
-                                     uint32_t starvationDelay) {
-  mStarvationDelay = PR_MillisecondsToInterval(starvationDelay);
-  if (favorPerfOverStarvation) {
-    ++mFavorPerf;
-  } else {
-    --mFavorPerf;
-    mSwitchTime = PR_IntervalNow();
+nsBaseAppShell::GeckoTaskBurst() {
+  if (mGeckoTaskBurstStartTime == 0) {
+    mGeckoTaskBurstStartTime = PR_IntervalNow();
   }
   return NS_OK;
 }
@@ -246,7 +239,9 @@ nsBaseAppShell::OnProcessNextEvent(nsIThreadInternal* thr, bool mayWait) {
   // NativeEventCallback to process gecko events.
   mProcessedGeckoEvents = false;
 
-  if (mFavorPerf <= 0 && start > mSwitchTime + mStarvationDelay) {
+  // Content processes always priorize gecko events.
+  if (!XRE_IsContentProcess() && (start > (mGeckoTaskBurstStartTime + limit))) {
+    mGeckoTaskBurstStartTime = 0;
     // Favor pending native events
     PRIntervalTime now = start;
     bool keepGoing;

widget/nsBaseAppShell.h

@@ -97,10 +97,8 @@ class nsBaseAppShell : public nsIAppShell,
    * have been consumed by the inner event loop(s).
    */
   bool* mBlockedWait;
-  int32_t mFavorPerf;
   mozilla::Atomic<bool> mNativeEventPending;
-  PRIntervalTime mStarvationDelay;
-  PRIntervalTime mSwitchTime;
+  PRIntervalTime mGeckoTaskBurstStartTime;
   PRIntervalTime mLastNativeEventTime;
   enum EventloopNestingState {
     eEventloopNone,   // top level thread execution

widget/nsIAppShell.idl

@@ -35,22 +35,11 @@ interface nsIAppShell : nsISupports
   void exit();
 
   /**
-   * Give hint to native event queue notification mechanism. If the native
-   * platform needs to tradeoff performance vs. native event starvation this
-   * hint tells the native dispatch code which to favor.  The default is to
-   * prevent native event starvation.
-   *
-   * Calls to this function may be nested. When the number of calls that pass
-   * PR_TRUE is subtracted from the number of calls that pass PR_FALSE is
-   * greater than 0, performance is given precedence over preventing event
-   * starvation.
-   *
-   * The starvationDelay arg is only used when favorPerfOverStarvation is
-   * PR_FALSE. It is the amount of time in milliseconds to wait before the
-   * PR_FALSE actually takes effect.
+   * Ask the native event queue notification mechanism to favor Gecko tasks
+   * (instead of native tasks) for a short while. (Content processes always
+   * favor Gecko tasks.)
    */
-  void favorPerformanceHint(in boolean favorPerfOverStarvation,
-                            in unsigned long starvationDelay);
+  void geckoTaskBurst();
 
   /**
    * Suspends the use of additional platform-specific methods (besides the