Implement evictFrames() to support MSE's coded frame eviction algorithm.

media/filters/source_buffer_stream.cc

Index: media/filters/source_buffer_stream.cc
diff --git a/media/filters/source_buffer_stream.cc b/media/filters/source_buffer_stream.cc
index faba8ec9d1e8d75832cd3ce30296e4c7b766397a..899d672e81a8641e5f9d9d581a2329b98d3913d6 100644
--- a/media/filters/source_buffer_stream.cc
+++ b/media/filters/source_buffer_stream.cc
@@ -348,8 +348,6 @@ bool SourceBufferStream::Append(const BufferQueue& buffers) {
 
   SetSelectedRangeIfNeeded(next_buffer_timestamp);
 
-  GarbageCollectIfNeeded();
-
   DVLOG(1) << __FUNCTION__ << " " << GetStreamTypeName()
            << ": done. ranges_=" << RangesToString(ranges_);
   DCHECK(IsRangeListSorted(ranges_));
@@ -583,7 +581,7 @@ void SourceBufferStream::SetConfigIds(const BufferQueue& buffers) {
   }
 }
 
-void SourceBufferStream::GarbageCollectIfNeeded() {
+bool SourceBufferStream::GarbageCollectIfNeeded(DecodeTimestamp media_time) {
   // Compute size of |ranges_|.
   int ranges_size = 0;
   for (RangeList::iterator itr = ranges_.begin(); itr != ranges_.end(); ++itr)
@@ -591,7 +589,7 @@ void SourceBufferStream::GarbageCollectIfNeeded() {
 
   // Return if we're under or at the memory limit.
   if (ranges_size <= memory_limit_)
-    return;
+    return true;
 
   int bytes_to_free = ranges_size - memory_limit_;
 
@@ -605,15 +603,16 @@ void SourceBufferStream::GarbageCollectIfNeeded() {
 
   // Begin deleting from the front.
   if (bytes_to_free - bytes_freed > 0)
-    bytes_freed += FreeBuffers(bytes_to_free - bytes_freed, false);
+    bytes_freed += FreeBuffers(bytes_to_free - bytes_freed, media_time, false);
 
-  // Begin deleting from the back.
   if (bytes_to_free - bytes_freed > 0)
-    bytes_freed += FreeBuffers(bytes_to_free - bytes_freed, true);
+    bytes_freed += FreeBuffers(bytes_to_free - bytes_freed, media_time, true);
 
   DVLOG(2) << __FUNCTION__ << " " << GetStreamTypeName() << ": After GC"
            << " bytes_freed=" << bytes_freed
            << " ranges_=" << RangesToString(ranges_);
+
+  return bytes_freed >= bytes_to_free;
 }
 
 int SourceBufferStream::FreeBuffersAfterLastAppended(int total_bytes_to_free) {
@@ -676,6 +675,7 @@ int SourceBufferStream::GetRemovalRange(
 }
 
 int SourceBufferStream::FreeBuffers(int total_bytes_to_free,
+                                    DecodeTimestamp media_time,
                                     bool reverse_direction) {
   TRACE_EVENT2("media", "SourceBufferStream::FreeBuffers",
                "total bytes to free", total_bytes_to_free,
@@ -707,6 +707,10 @@ int SourceBufferStream::FreeBuffers(int total_bytes_to_free,
         DCHECK_EQ(current_range, selected_range_);
         break;
       }
+      if (media_time != kNoDecodeTimestamp() &&
+          !current_range->FirstGOPEarlierThanMediaTime(media_time)) {
+        break;
+      }
       bytes_deleted = current_range->DeleteGOPFromFront(&buffers);
     }
 
@@ -715,6 +719,7 @@ int SourceBufferStream::FreeBuffers(int total_bytes_to_free,
     if (end_timestamp == last_appended_buffer_timestamp_) {
       DCHECK(last_appended_buffer_timestamp_ != kNoDecodeTimestamp());
       DCHECK(!new_range_for_append);
+
       // Create a new range containing these buffers.
       new_range_for_append = new SourceBufferRange(
           TypeToGapPolicy(GetType()),
@@ -734,6 +739,11 @@ int SourceBufferStream::FreeBuffers(int total_bytes_to_free,
       delete current_range;
       reverse_direction ? ranges_.pop_back() : ranges_.pop_front();
     }
+
+    if (reverse_direction && new_range_for_append) {
+      // We don't want to delete any further, or we'll be creating gaps
+      break;
+    }
   }
 
   // Insert |new_range_for_append| into |ranges_|, if applicable.