Fire canplaythrough as soon as download defers to fix autoplay

media/base/download_rate_monitor.cc

Index: media/base/download_rate_monitor.cc
diff --git a/media/base/download_rate_monitor.cc b/media/base/download_rate_monitor.cc
index f27b2e8059223c6425ba1f3b5c0651e5e19e59d5..eaf93bb42e3fccdf3f35e51684f59bb7c3d6cd0d 100644
--- a/media/base/download_rate_monitor.cc
+++ b/media/base/download_rate_monitor.cc
@@ -120,12 +120,18 @@ void DownloadRateMonitor::SetBufferedBytes(
 }
 
 void DownloadRateMonitor::SetNetworkActivity(bool is_downloading_data) {
-  if (is_downloading_data == is_downloading_data_)
-    return;
   // Invalidate the current sample if downloading is going from start to stopped
   // or vice versa.
-  current_sample_.Reset();
-  is_downloading_data_ = is_downloading_data;
+  if (is_downloading_data != is_downloading_data_) {
+    current_sample_.Reset();
+    is_downloading_data_ = is_downloading_data;
+  }
+
+  // Record when download defers for the first time.
+  if (!is_downloading_data && !has_deferred_) {
+    has_deferred_ = true;
+    NotifyCanPlayThroughIfNeeded();
+  }
 }
 
 void DownloadRateMonitor::Stop() {
@@ -146,6 +152,7 @@ void DownloadRateMonitor::Reset() {
   bitrate_ = 0;
   stopped_ = true;
   streaming_ = false;
+  has_deferred_ = false;
 }
 
 DownloadRateMonitor::~DownloadRateMonitor() { }
@@ -210,8 +217,9 @@ bool DownloadRateMonitor::ShouldNotifyCanPlayThrough() {
   if (local_source_ || streaming_)
     return true;
 
-  // If all bytes are buffered, fire CanPlayThrough.
-  if (buffered_bytes_ == total_bytes_)
+  // If all bytes are buffered or if enough bytes were buffered such that
+  // downloading has deferred, fire CanPlayThrough.
+  if (buffered_bytes_ == total_bytes_ || has_deferred_)
     return true;
 
   // If bitrate is unknown, optimistically fire CanPlayThrough immediately.
@@ -228,12 +236,9 @@ bool DownloadRateMonitor::ShouldNotifyCanPlayThrough() {
   if (download_rate > 0)
     return download_rate >= bytes_needed_per_second;
 
-  // If download rate is unknown, it may be because the media is being
-  // downloaded so fast that it cannot collect an adequate number of samples
-  // before the download gets deferred.
-  //
-  // To catch this case, we also look at how much data is being downloaded
-  // immediately after the download begins.
+  // With very fast connections, we may want to fire CanPlayThrough before
+  // waiting for the sample window size to reach |kNumberOfSamples|. Check for
+  // this scenario.
   if (sample_window_.size() < kNumberOfSamples) {
     int64 bytes_downloaded_since_start =
         bytes_downloaded_in_window() + current_sample_.bytes_downloaded();