preload=metadata loads a little instead of none

Change the multibuffer code to preload 1/32th of the normal preload
when "preload=metadata" is used. This should work around problems
that occur because WMPI says we have enough data while the demuxer
may still be filling buffers.

For a lot of videos, this means we'll be preloading 64k.

Bug: 814328
Change-Id: Iae6945d63bf8298975eb51eda22b16189c7658df
Reviewed-on: https://chromium-review.googlesource.com/937997
Commit-Queue: Fredrik Hubinette <hubbe@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#539911}

media/blink/multibuffer_data_source.cc

@@ -24,6 +24,14 @@ const int64_t kMinBufferPreload = 2 << 20;  // 2 Mb
 // Maxmimum preload buffer.
 const int64_t kMaxBufferPreload = 50 << 20;  // 50 Mb
 
+// If preload_ == METADATA, preloading size will be
+// shifted down this many bits. This shift turns
+// one Mb into one 32k block.
+// This seems to be the smallest amount of preload we can do without
+// ending up repeatedly closing and re-opening the connection
+// due to read calls after OnBufferingHaveEnough have been called.
+const int64_t kMetadataShift = 6;
+
 // Preload this much extra, then stop preloading until we fall below the
 // kTargetSecondsBufferedAhead.
 const int64_t kPreloadHighExtra = 1 << 20;  // 1 Mb
@@ -168,6 +176,7 @@ void MultibufferDataSource::CreateResourceLoader(int64_t first_byte_position,
   SetReader(new MultiBufferReader(
       url_data_->multibuffer(), first_byte_position, last_byte_position,
       base::Bind(&MultibufferDataSource::ProgressCallback, weak_ptr_)));
+  reader_->SetIsClientAudioElement(is_client_audio_element_);
   UpdateBufferSizes();
 }
 
@@ -191,7 +200,6 @@ void MultibufferDataSource::Initialize(const InitializeCB& init_cb) {
   init_cb_ = init_cb;
 
   CreateResourceLoader(0, kPositionNotSpecified);
-  reader_->SetIsClientAudioElement(is_client_audio_element_);
 
   // We're not allowed to call Wait() if data is already available.
   if (reader_->Available()) {
@@ -752,10 +760,10 @@ void MultibufferDataSource::UpdateBufferSizes() {
   reader_->SetPinRange(pin_backward, pin_forward);
 
   if (preload_ == METADATA) {
-    reader_->SetPreload(0, 0);
-  } else {
-    reader_->SetPreload(preload_high, preload);
+    preload_high >>= kMetadataShift;
+    preload >>= kMetadataShift;
   }
+  reader_->SetPreload(preload_high, preload);
 }
 
 }  // namespace media

media/blink/multibuffer_data_source_unittest.cc

@@ -389,8 +389,8 @@ class MultibufferDataSourceTest : public testing::Test {
   }
 
   void CheckReadThenDefer() {
-    EXPECT_EQ(0, preload_low());
-    EXPECT_EQ(0, preload_high());
+    EXPECT_EQ(2 << 14, preload_low());
+    EXPECT_EQ(3 << 14, preload_high());
   }
 
   void CheckNeverDefer() {
@@ -1180,6 +1180,9 @@ TEST_F(MultibufferDataSourceTest, ExternalResource_Response206_VerifyDefer) {
   EXPECT_CALL(*this, ReadCallback(kDataSize));
   ReadAt(0);
 
+  EXPECT_CALL(host_, AddBufferedByteRange(0, kDataSize * 2));
+  ReceiveData(kDataSize);
+
   ASSERT_TRUE(active_loader());
   EXPECT_TRUE(data_provider()->deferred());
 }
@@ -1204,6 +1207,12 @@ TEST_F(MultibufferDataSourceTest,
   EXPECT_CALL(host_, AddBufferedByteRange(0, kDataSize * 2));
   ReceiveData(kDataSize);
 
+  EXPECT_CALL(host_, AddBufferedByteRange(0, kDataSize * 3));
+  ReceiveData(kDataSize);
+
+  EXPECT_CALL(host_, AddBufferedByteRange(0, kDataSize * 4));
+  ReceiveData(kDataSize);
+
   EXPECT_FALSE(active_loader_allownull());
 }
 
@@ -1230,10 +1239,17 @@ TEST_F(MultibufferDataSourceTest,
 
   ReceiveDataLow(2000);
   EXPECT_CALL(host_, AddBufferedByteRange(0, kDataSize * 2 + 2000));
+  EXPECT_CALL(host_, AddBufferedByteRange(kDataSize * 2, kDataSize * 2 + 2000));
   ReceiveDataLow(kDataSize);
 
   base::RunLoop().RunUntilIdle();
 
+  EXPECT_CALL(host_, AddBufferedByteRange(0, kDataSize * 3 + 2000));
+  ReceiveData(kDataSize);
+
+  EXPECT_CALL(host_, AddBufferedByteRange(0, kDataSize * 4 + 2000));
+  ReceiveData(kDataSize);
+
   EXPECT_FALSE(active_loader_allownull());
 }
 

third_party/WebKit/LayoutTests/SlowTests

@@ -142,6 +142,8 @@ crbug.com/680917 http/tests/devtools/audits2/ [ Slow ]
 
 # This test is intentionally SLOW as we're waiting for a connection timeout.
 crbug.com/73609 http/tests/media/video-play-stall.html [ Slow ]
+# This test is intentionally SLOW because of throttled loading.
+crbug.com/73609 http/tests/media/video-preload-metadata.html [ Slow ]
 
 # Many of the virtual animations tests are slow.
 crbug.com/311482 virtual/threaded/animations/prefixed/keyframes-unprefixed-03.html [ Slow ]