Reland "Improve suspending logic."

This is a reland of d2506f13
Original change's description:
> Improve suspending logic.
> 
> When loading takes too long, we can suspend the codec before
> we have a chance to load the first frame. This is all normal,
> but should only happen when we are waiting on the network.
> This CL makes sure that we have additional progress callbacks
> expected before suspending.
> 
> Bug: 728468
> Change-Id: I815520e0ba832617b04948f7fbefb88498cf79b7
> Reviewed-on: https://chromium-review.googlesource.com/614360
> Reviewed-by: Dan Sanders <sandersd@chromium.org>
> Commit-Queue: Fredrik Hubinette <hubbe@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#494212}

Bug: 728468
Change-Id: Ide175e6e5c8d2ecaeeb81b0055352f66c917d099
Reviewed-on: https://chromium-review.googlesource.com/627616Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Fredrik Hubinette <hubbe@chromium.org>
Cr-Commit-Position: refs/heads/master@{#496513}

media/blink/buffered_data_source_host_impl.cc

@@ -57,12 +57,9 @@ int64_t BufferedDataSourceHostImpl::UnloadedBytesInInterval(
 void BufferedDataSourceHostImpl::AddBufferedByteRange(int64_t start,
                                                       int64_t end) {
   int64_t new_bytes = UnloadedBytesInInterval(Interval<int64_t>(start, end));
-  if (new_bytes == 0) {
-    // No change
-    return;
-  }
+  if (new_bytes > 0)
+    did_loading_progress_ = true;
   buffered_byte_ranges_.SetInterval(start, end, 1);
-  did_loading_progress_ = true;
 
   base::TimeTicks now = tick_clock_->NowTicks();
   int64_t bytes_so_far = 0;

media/blink/webmediaplayer_impl.cc

@@ -938,6 +938,16 @@ bool WebMediaPlayerImpl::IsPrerollAttemptNeeded() {
   if (highest_ready_state_ >= ReadyState::kReadyStateHaveFutureData)
     return false;
 
+  // To suspend before we reach kReadyStateHaveCurrentData is only ok
+  // if we know we're going to get woken up when we get more data, which
+  // will only happen if the network is in the "Loading" state.
+  // This happens when the network is fast, but multiple videos are loading
+  // and multiplexing gets held up waiting for available threads.
+  if (highest_ready_state_ <= ReadyState::kReadyStateHaveMetadata &&
+      network_state_ != WebMediaPlayer::kNetworkStateLoading) {
+    return true;
+  }
+
   if (preroll_attempt_pending_)
     return true;
 

media/blink/webmediaplayer_impl_unittest.cc

@@ -270,6 +270,9 @@ class WebMediaPlayerImplTest : public testing::Test {
   }
 
  protected:
+  void SetNetworkState(blink::WebMediaPlayer::NetworkState state) {
+    wmpi_->SetNetworkState(state);
+  }
   void SetReadyState(blink::WebMediaPlayer::ReadyState state) {
     wmpi_->SetReadyState(state);
   }
@@ -427,11 +430,9 @@ TEST_F(WebMediaPlayerImplTest, ConstructAndDestroy) {
   EXPECT_FALSE(IsSuspended());
 }
 
-TEST_F(WebMediaPlayerImplTest, IdleSuspendIsEnabledBeforeLoadingBegins) {
+TEST_F(WebMediaPlayerImplTest, IdleSuspendBeforeLoadingBegins) {
   InitializeWebMediaPlayerImpl();
-  EXPECT_TRUE(delegate_.ExpireForTesting());
-  base::RunLoop().RunUntilIdle();
-  EXPECT_TRUE(IsSuspended());
+  EXPECT_FALSE(delegate_.ExpireForTesting());
 }
 
 TEST_F(WebMediaPlayerImplTest,
@@ -451,6 +452,7 @@ TEST_F(WebMediaPlayerImplTest,
 
 TEST_F(WebMediaPlayerImplTest, IdleSuspendIsEnabledIfLoadingHasStalled) {
   InitializeWebMediaPlayerImpl();
+  SetNetworkState(blink::WebMediaPlayer::kNetworkStateLoading);
   base::SimpleTestTickClock* clock = new base::SimpleTestTickClock();
   clock->Advance(base::TimeDelta::FromSeconds(1));
   SetTickClock(clock);
@@ -466,6 +468,7 @@ TEST_F(WebMediaPlayerImplTest, IdleSuspendIsEnabledIfLoadingHasStalled) {
 TEST_F(WebMediaPlayerImplTest, DidLoadingProgressTriggersResume) {
   // Same setup as IdleSuspendIsEnabledBeforeLoadingBegins.
   InitializeWebMediaPlayerImpl();
+  SetNetworkState(blink::WebMediaPlayer::kNetworkStateLoading);
   EXPECT_TRUE(delegate_.ExpireForTesting());
   base::RunLoop().RunUntilIdle();
   EXPECT_TRUE(IsSuspended());