[SurfaceFlinger] fix permanently enabling early offsets.

* Add notion of intended period in DispSync, and use that to detect
whether the simulated period will be changed.
* Propagate that signal to setDesiredActiveConfig, so that we don't fall
into early offsets unnecessarily, which can cause early offsets to
always be enabled.

Bug: 132678707
Test: systrace
Test: swappy test app
Test: scrolling through google news
Change-Id: I18df1b9d949cd534ecbf1c8891b6f88eab8be399
diff --git a/services/surfaceflinger/Scheduler/Scheduler.h b/services/surfaceflinger/Scheduler/Scheduler.h
index 96d4bd5..f6cc87b 100644
--- a/services/surfaceflinger/Scheduler/Scheduler.h
+++ b/services/surfaceflinger/Scheduler/Scheduler.h
@@ -135,13 +135,18 @@
 
     void enableHardwareVsync();
     void disableHardwareVsync(bool makeUnavailable);
+    // Resyncs the scheduler to hardware vsync.
+    // If makeAvailable is true, then hardware vsync will be turned on.
+    // Otherwise, if hardware vsync is not already enabled then this method will
+    // no-op.
+    // The period is the vsync period from the current display configuration.
     void resyncToHardwareVsync(bool makeAvailable, nsecs_t period);
     // Creates a callback for resyncing.
     ResyncCallback makeResyncCallback(GetVsyncPeriod&& getVsyncPeriod);
     void setRefreshSkipCount(int count);
-    // Passes a vsync sample to DispSync. periodChange will be true if DipSync
-    // detected that the vsync period changed, and false otherwise.
-    void addResyncSample(const nsecs_t timestamp, bool* periodChanged);
+    // Passes a vsync sample to DispSync. periodFlushed will be true if
+    // DispSync detected that the vsync period changed, and false otherwise.
+    void addResyncSample(const nsecs_t timestamp, bool* periodFlushed);
     void addPresentFence(const std::shared_ptr<FenceTime>& fenceTime);
     void setIgnorePresentFences(bool ignore);
     nsecs_t expectedPresentTime();