Add support for partial append window end trimming.

media/filters/frame_processor_unittest.cc

Index: media/filters/frame_processor_unittest.cc
diff --git a/media/filters/frame_processor_unittest.cc b/media/filters/frame_processor_unittest.cc
index f4cde5a1c0c3ba22368e734060af241b6106f05a..d6cabf0446b7238baddd379fe044f1db08f0e1a1 100644
--- a/media/filters/frame_processor_unittest.cc
+++ b/media/filters/frame_processor_unittest.cc
@@ -607,6 +607,19 @@ TEST_P(FrameProcessorTest, AppendWindowFilterWithInexactPreroll) {
   CheckReadsThenReadStalls(audio_.get(), "0P 0:9.75 10:20");
 }
 
+TEST_P(FrameProcessorTest, AppendWindowFilterWithInexactPreroll_2) {
+  InSequence s;
+  AddTestTracks(HAS_AUDIO);
+  new_media_segment_ = true;
+  if (GetParam())
+    frame_processor_->SetSequenceMode(true);
+  SetTimestampOffset(-frame_duration_);
+  EXPECT_CALL(callbacks_, PossibleDurationIncrease(frame_duration_ * 2));
+  ProcessFrames("0K 10.25K 20K", "");
+  CheckExpectedRangesByTimestamp(audio_.get(), "{ [0,20) }");
+  CheckReadsThenReadStalls(audio_.get(), "0P 0:10.25 10:20");
+}
+
 TEST_P(FrameProcessorTest, AllowNegativeFramePTSAndDTSBeforeOffsetAdjustment) {
   InSequence s;
   AddTestTracks(HAS_AUDIO);