Enhance WebMediaPlayer::buffered() to account for evicted ranges.

media/blink/webmediaplayer_impl.cc

Index: media/blink/webmediaplayer_impl.cc
diff --git a/media/blink/webmediaplayer_impl.cc b/media/blink/webmediaplayer_impl.cc
index 0fd74e8390402a15d3cc42dd6a12370e7555c171..091df700029f2c24c55aa01af6ba64572a25e780 100644
--- a/media/blink/webmediaplayer_impl.cc
+++ b/media/blink/webmediaplayer_impl.cc
@@ -478,9 +478,25 @@ blink::WebTimeRanges WebMediaPlayerImpl::buffered() const {
 
   const base::TimeDelta duration = pipeline_.GetMediaDuration();
   if (duration != kInfiniteDuration()) {
-    buffered_data_source_host_.AddBufferedTimeRanges(
-        &buffered_time_ranges, duration);
+    // Demuxed ranges are not useful for a streaming resource, since we can't
+    // actually seek to those points unless they're cached.  Instead report
+    // buffered() based on the lowest cached byte range.
+    //
+    // Technically we could do this for non-streaming resources too since we're
+    // caching the same amount for them, but the returned range will be shown on
+    // the controls and historically there's been outcry when gaps are shown.
+    if (data_source_ && data_source_->IsStreaming()) {
+      Ranges<base::TimeDelta> cached_ranges;
+      buffered_data_source_host_.AddBufferedTimeRanges(&cached_ranges,
+                                                       duration);
+      buffered_time_ranges =
+          buffered_time_ranges.IntersectionWith(cached_ranges);
+    } else {
+      buffered_data_source_host_.AddBufferedTimeRanges(&buffered_time_ranges,
+                                                       duration);
+    }
   }
+
   return ConvertToWebTimeRanges(buffered_time_ranges);
 }