Map the Android VsyncWaiter frame start time to the clock used by fml::TimePoint (#29093)

Author: jason-simmons

shell/platform/android/io/flutter/embedding/engine/FlutterJNI.java

@@ -238,7 +238,7 @@ private static void asyncWaitForVsync(final long cookie) {
 
   // TODO(mattcarroll): add javadocs
   public static native void nativeOnVsync(
-      long frameTimeNanos, long frameTargetTimeNanos, long cookie);
+      long frameDelayNanos, long refreshPeriodNanos, long cookie);
 
   // TODO(mattcarroll): add javadocs
   @NonNull

shell/platform/android/io/flutter/view/VsyncWaiter.java

@@ -21,6 +21,7 @@ public static VsyncWaiter getInstance(float fps) {
   }
 
   private final float fps;
+  private final long refreshPeriodNanos;
 
   private final FlutterJNI.AsyncWaitForVsyncDelegate asyncWaitForVsyncDelegate =
       new FlutterJNI.AsyncWaitForVsyncDelegate() {
@@ -31,16 +32,19 @@ public void asyncWaitForVsync(long cookie) {
                   new Choreographer.FrameCallback() {
                     @Override
                     public void doFrame(long frameTimeNanos) {
-                      long refreshPeriodNanos = (long) (1000000000.0 / fps);
-                      FlutterJNI.nativeOnVsync(
-                          frameTimeNanos, frameTimeNanos + refreshPeriodNanos, cookie);
+                      long delay = System.nanoTime() - frameTimeNanos;
+                      if (delay < 0) {
+                        delay = 0;
+                      }
+                      FlutterJNI.nativeOnVsync(delay, refreshPeriodNanos, cookie);
                     }
                   });
         }
       };
 
   private VsyncWaiter(float fps) {
     this.fps = fps;
+    refreshPeriodNanos = (long) (1000000000.0 / fps);
   }
 
   public void init() {

shell/platform/android/vsync_waiter_android.cc

@@ -41,15 +41,15 @@ void VsyncWaiterAndroid::AwaitVSync() {
 // static
 void VsyncWaiterAndroid::OnNativeVsync(JNIEnv* env,
                                        jclass jcaller,
-                                       jlong frameTimeNanos,
-                                       jlong frameTargetTimeNanos,
+                                       jlong frameDelayNanos,
+                                       jlong refreshPeriodNanos,
                                        jlong java_baton) {
   TRACE_EVENT0("flutter", "VSYNC");
 
-  auto frame_time = fml::TimePoint::FromEpochDelta(
-      fml::TimeDelta::FromNanoseconds(frameTimeNanos));
-  auto target_time = fml::TimePoint::FromEpochDelta(
-      fml::TimeDelta::FromNanoseconds(frameTargetTimeNanos));
+  auto frame_time =
+      fml::TimePoint::Now() - fml::TimeDelta::FromNanoseconds(frameDelayNanos);
+  auto target_time =
+      frame_time + fml::TimeDelta::FromNanoseconds(refreshPeriodNanos);
 
   ConsumePendingCallback(java_baton, frame_time, target_time);
 }

shell/platform/android/vsync_waiter_android.h

@@ -28,8 +28,8 @@ class VsyncWaiterAndroid final : public VsyncWaiter {
 
   static void OnNativeVsync(JNIEnv* env,
                             jclass jcaller,
-                            jlong frameTimeNanos,
-                            jlong frameTargetTimeNanos,
+                            jlong frameDelayNanos,
+                            jlong refreshPeriodNanos,
                             jlong java_baton);
 
   static void ConsumePendingCallback(jlong java_baton,