sf: Construct Phase Offsets for unknown fps

External display can support a Refresh Rate value which doesn't exist
in keys of mOffsets map which has been created with RefreshRateConfigs
of Primary display, based on current design. This is not a fatal error
scenario. In such a case, construct Phase Offsets with current logic.

CRs-Fixed: 2643508
Bug: 151859083
Test: boot
Change-Id: Ib89f0dbc3db6bdd3e41681c31c567890487c453f
diff --git a/services/surfaceflinger/Scheduler/PhaseOffsets.h b/services/surfaceflinger/Scheduler/PhaseOffsets.h
index b7d4eae..208f06b 100644
--- a/services/surfaceflinger/Scheduler/PhaseOffsets.h
+++ b/services/surfaceflinger/Scheduler/PhaseOffsets.h
@@ -69,8 +69,9 @@
 private:
     std::unordered_map<float, Offsets> initializeOffsets(
             const scheduler::RefreshRateConfigs&) const;
-    Offsets getDefaultOffsets(nsecs_t vsyncDuration) const;
-    Offsets getHighFpsOffsets(nsecs_t vsyncDuration) const;
+    Offsets getDefaultOffsets(nsecs_t vsyncPeriod) const;
+    Offsets getHighFpsOffsets(nsecs_t vsyncPeriod) const;
+    Offsets getPhaseOffsets(float fps, nsecs_t vsyncPeriod) const;
 
     const nsecs_t mThresholdForNextVsync;
     const std::unordered_map<float, Offsets> mOffsets;