MediaSource: Fix CHECK crash in append fudge room edge case.

media/filters/source_buffer_stream_unittest.cc

Index: media/filters/source_buffer_stream_unittest.cc
diff --git a/media/filters/source_buffer_stream_unittest.cc b/media/filters/source_buffer_stream_unittest.cc
index 4f37509837ca30201248647affab1b5c4ecf6ab6..e47baa8a60f7ac229a54f65ea0f3d0521b4bcf06 100644
--- a/media/filters/source_buffer_stream_unittest.cc
+++ b/media/filters/source_buffer_stream_unittest.cc
@@ -3320,6 +3320,56 @@ TEST_F(SourceBufferStreamTest, SetExplicitDuration_EdgeCase) {
   CheckExpectedRanges("{ [10,19) }");
 }
 
+TEST_F(SourceBufferStreamTest, SetExplicitDuration_EdgeCase2) {

[wolenetz, 2016/10/05 22:41:09]

FWIW, EdgeCase2 exercises deprecated path currently. Once "duration reduction
can truncate buffered frames" is disallowed (as is already disallowed in spec),
this test will need to just be dropped (but keep RemoveWithinFudgeRoom, below).

+  // This test requires specific relative proportions for fudge room, append
+  // size, and duration truncation amounts. See details at:
+  // https://codereview.chromium.org/2385423002
+
+  // Append buffers with first buffer establishing max_inter_buffer_distance
+  // of 5 ms. This translates to a fudge room (2 x max_interbuffer_distance) of
+  // 10 ms.
+  NewCodedFrameGroupAppend("0K 5K 9D4K");
+  CheckExpectedRangesByTimestamp("{ [0,13) }");
+
+  // Trim off last 2 buffers, totaling 8 ms. Notably less than the current fudge
+  // room of 10 ms.
+  stream_->OnSetDuration(base::TimeDelta::FromMilliseconds(5));
+
+  // Verify truncation.
+  CheckExpectedRangesByTimestamp("{ [0,5) }");
+
+  // Append new buffers just beyond the fudge-room allowance of 10ms.
+  AppendBuffers("11K 15K");
+
+  // Verify new append creates a gap.
+  CheckExpectedRangesByTimestamp("{ [0,5) [11,19) }");
+}
+
+TEST_F(SourceBufferStreamTest, RemoveWithinFudgeRoom) {
+  // This test requires specific relative proportions for fudge room, append
+  // size, and removal amounts. See details at:
+  // https://codereview.chromium.org/2385423002
+
+  // Append buffers with first buffer establishing max_inter_buffer_distance
+  // of 5 ms. This translates to a fudge room (2 x max_interbuffer_distance) of
+  // 10 ms.
+  NewCodedFrameGroupAppend("0K 5K 9D4K");
+  CheckExpectedRangesByTimestamp("{ [0,13) }");
+
+  // Trim off last 2 buffers, totaling 8 ms. Notably less than the current fudge
+  // room of 10 ms.
+  RemoveInMs(5, 13, 13);
+
+  // Verify removal.
+  CheckExpectedRangesByTimestamp("{ [0,5) }");
+
+  // Append new buffers just beyond the fudge-room allowance of 10ms.
+  AppendBuffers("11K 15K");
+
+  // Verify new append creates a gap.
+  CheckExpectedRangesByTimestamp("{ [0,5) [11,19) }");
+}
+
 TEST_F(SourceBufferStreamTest, SetExplicitDuration_DeletePartialRange) {
   // Append 5 buffers at positions 0 through 4.
   NewCodedFrameGroupAppend(0, 5);
@@ -4726,6 +4776,7 @@ TEST_F(SourceBufferStreamTest,
   SignalStartOfCodedFrameGroup(base::TimeDelta::FromMilliseconds(45));
   CheckExpectedRangesByTimestamp("{ [0,60) }");
 
+  LOG(ERROR) << "-------------SECOND APPEND------------";

[wolenetz, 2016/10/05 22:41:09]

nit: needed?

[chcunningham, 2016/10/06 21:57:33]

Woops. Removed.

   AppendBuffers("2000K 2010");
   CheckExpectedRangesByTimestamp("{ [0,2020) }");
   Seek(0);
@@ -4748,12 +4799,14 @@ TEST_F(SourceBufferStreamTest,
 }
 
 TEST_F(SourceBufferStreamTest,
-       StartCodedFrameGroup_InExisting_RemoveGOP_ThenAppend_2) {
+       StartCodedFrameGroup_InExisting_RemoveGOP_ThenAppend_2n) {

[wolenetz, 2016/10/05 22:41:09]

nit: s/2n/2/ ?

[chcunningham, 2016/10/06 21:57:33]

Done.

   NewCodedFrameGroupAppend("0K 10 20 30K 40 50");
   SignalStartOfCodedFrameGroup(base::TimeDelta::FromMilliseconds(45));
+  LOG(ERROR) << "---REMOVING FROM 30 - 60 ---";

[wolenetz, 2016/10/05 22:41:09]

nit ditto

[chcunningham, 2016/10/06 21:57:33]

Done.

   RemoveInMs(30, 60, 60);
   CheckExpectedRangesByTimestamp("{ [0,30) }");
 
+  LOG(ERROR) << "---SECOND APPEND---";

[wolenetz, 2016/10/05 22:41:09]

nit ditto

[chcunningham, 2016/10/06 21:57:33]

Done.

   AppendBuffers("2000K 2010");
   CheckExpectedRangesByTimestamp("{ [0,30) [45,2020) }");
   Seek(0);