Enable HTTP/2 to use a LIFO scheduler to schedule write.

This CL lands server change 152524616 by yasong.

BUG=488484

Review-Url: https://codereview.chromium.org/2844963005
Cr-Commit-Position: refs/heads/master@{#467971}

net/spdy/core/lifo_write_scheduler.h

@@ -69,8 +69,7 @@ class LifoWriteScheduler : public WriteScheduler<StreamIdType> {
   }
 
   bool ShouldYield(StreamIdType stream_id) const override {
-    // stream_id is not necessary to be on the ready list.
-    return stream_id < *ready_streams_.rbegin();
+    return !ready_streams_.empty() && stream_id < *ready_streams_.rbegin();
   }
 
   void MarkStreamReady(StreamIdType stream_id, bool /*add_to_front*/) override;
@@ -106,6 +105,7 @@ void LifoWriteScheduler<StreamIdType>::UnregisterStream(
     return;
   }
   registered_streams_.erase(stream_id);
+  ready_streams_.erase(stream_id);
 }
 
 template <typename StreamIdType>
@@ -161,7 +161,7 @@ void LifoWriteScheduler<StreamIdType>::MarkStreamReady(StreamIdType stream_id,
     return;
   }
   if (ready_streams_.find(stream_id) != ready_streams_.end()) {
-    SPDY_BUG << "Stream already exists in the list";
+    VLOG(1) << "Stream already exists in the list";
     return;
   }
   ready_streams_.insert(stream_id);
@@ -172,7 +172,7 @@ void LifoWriteScheduler<StreamIdType>::MarkStreamNotReady(
     StreamIdType stream_id) {
   auto it = ready_streams_.find(stream_id);
   if (it == ready_streams_.end()) {
-    SPDY_BUG << "Try to remove a stream that is not on list";
+    VLOG(1) << "Try to remove a stream that is not on list";
     return;
   }
   ready_streams_.erase(it);

net/spdy/core/lifo_write_scheduler_test.cc

@@ -61,12 +61,11 @@ TEST(LifoWriteSchedulerTest, ReadyListTest) {
   EXPECT_TRUE(lifo.HasReadyStreams());
   EXPECT_EQ((uint32_t)7, lifo.NumReadyStreams());
 
-  EXPECT_SPDY_BUG(lifo.MarkStreamReady(11, true),
-                  "Stream already exists in the list");
-  EXPECT_SPDY_BUG(lifo.MarkStreamNotReady(5),
-                  "Try to remove a stream that is not on list");
-  EXPECT_SPDY_BUG(lifo.MarkStreamNotReady(21),
-                  "Try to remove a stream that is not on list");
+  // Verify MarkStream(Not)Ready() can be called multiple times for the same
+  // stream.
+  lifo.MarkStreamReady(11, true);
+  lifo.MarkStreamNotReady(5);
+  lifo.MarkStreamNotReady(21);
 
   EXPECT_EQ((uint32_t)17, lifo.PopNextReadyStream());
   EXPECT_EQ((uint32_t)15, std::get<0>(lifo.PopNextReadyStreamAndPrecedence()));
@@ -81,6 +80,10 @@ TEST(LifoWriteSchedulerTest, ReadyListTest) {
   lifo.MarkStreamNotReady(7);
   EXPECT_TRUE(peer.GetReadyList()->find(7) == peer.GetReadyList()->end());
   EXPECT_EQ((uint32_t)2, lifo.NumReadyStreams());
+
+  lifo.MarkStreamNotReady(9);
+  lifo.MarkStreamNotReady(11);
+  EXPECT_FALSE(lifo.ShouldYield(1));
 }
 
 // Test add and remove from registered list.