Prevent incorrect start time from being used during new range creation.

If a SourceBuffer::Remove() call removed the GOP that is currently being
appended, an incorrect start timestamp would be used when the next GOP was
appended. This ultimately led to a crash if a followup Remove() call
ended up deleting the range. This change fixes the code that determines
the start timestamp for the range created for the second GOP.

BUG=382815
TEST=SourceBufferStreamTest, Remove_WholeGOPBeingAppended

Review URL: https://codereview.chromium.org/324223003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@276471 0039d316-1c4b-4281-b951-d872f2087c98

media/filters/source_buffer_stream.cc

@@ -503,7 +503,7 @@ bool SourceBufferStream::Append(const BufferQueue& buffers) {
     // segment, then we must make sure that we start with a keyframe.
     // This can happen if the GOP in the previous append gets destroyed
     // by a Remove() call.
-    if (!new_media_segment_ && !buffers.front()->IsKeyframe()) {
+    if (!new_media_segment_) {
       BufferQueue::const_iterator itr = buffers.begin();
 
       // Scan past all the non-keyframes.
@@ -517,15 +517,17 @@ bool SourceBufferStream::Append(const BufferQueue& buffers) {
         last_appended_buffer_timestamp_ = buffers.back()->GetDecodeTimestamp();
         last_appended_buffer_is_keyframe_ = buffers.back()->IsKeyframe();
         return true;
-      }
-
-      // Copy the first keyframe and everything after it into |trimmed_buffers|.
+      } else if (itr != buffers.begin()) {
+        // Copy the first keyframe and everything after it into
+        // |trimmed_buffers|.
         trimmed_buffers.assign(itr, buffers.end());
-
-      new_range_start_time = trimmed_buffers.front()->GetDecodeTimestamp();
         buffers_for_new_range = &trimmed_buffers;
       }
 
+      new_range_start_time =
+          buffers_for_new_range->front()->GetDecodeTimestamp();
+    }
+
     range_for_next_append_ =
         AddToRanges(new SourceBufferRange(
             GetType(), *buffers_for_new_range, new_range_start_time,
@@ -1619,6 +1621,8 @@ void SourceBufferStream::DeleteAndRemoveRange(RangeList::iterator* itr) {
   if (*itr == range_for_next_append_) {
     DVLOG(1) << __FUNCTION__ << " deleting range_for_next_append_.";
     range_for_next_append_ = ranges_.end();
+    last_appended_buffer_timestamp_ = kNoTimestamp();
+    last_appended_buffer_is_keyframe_ = false;
   }
 
   delete **itr;

media/filters/source_buffer_stream_unittest.cc

@@ -3511,6 +3511,33 @@ TEST_F(SourceBufferStreamTest, Remove_GOPBeingAppended) {
   CheckExpectedBuffers("240K 270 300");
 }
 
+TEST_F(SourceBufferStreamTest, Remove_WholeGOPBeingAppended) {
+  Seek(0);
+  NewSegmentAppend("0K 30 60 90");
+  CheckExpectedRangesByTimestamp("{ [0,120) }");
+
+  // Remove the keyframe of the current GOP being appended.
+  RemoveInMs(0, 30, 120);
+  CheckExpectedRangesByTimestamp("{ }");
+
+  // Continue appending the current GOP.
+  AppendBuffers("210 240");
+
+  CheckExpectedRangesByTimestamp("{ }");
+
+  // Append the beginning of the next GOP.
+  AppendBuffers("270K 300");
+
+  // Verify that the new range is started at the
+  // beginning of the next GOP.
+  CheckExpectedRangesByTimestamp("{ [270,330) }");
+
+  // Verify the buffers in the ranges.
+  CheckNoNextBuffer();
+  SeekToTimestamp(base::TimeDelta::FromMilliseconds(270));
+  CheckExpectedBuffers("270K 300");
+}
+
 TEST_F(SourceBufferStreamTest,
        Remove_PreviousAppendDestroyedAndOverwriteExistingRange) {
   SeekToTimestamp(base::TimeDelta::FromMilliseconds(90));