Make http/tests/media/audio-seekable-contains-zero-without-ranges.html work with multibuffers.

media/blink/multibuffer_data_source.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/blink/multibuffer_data_source.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/callback_helpers.h"
@@ skipping 378 matching lines @@
   int64_t available = reader_->Available();
   if (available < 0) {
     // A failure has occured.
     ReadOperation::Run(std::move(read_op_), kReadError);
     return;
   }
   if (available) {
     bytes_read =
         static_cast<int>(std::min<int64_t>(available, read_op_->size()));
     bytes_read = reader_->TryRead(read_op_->data(), bytes_read);
+
+    if (bytes_read == 0 && total_bytes_ == kPositionNotSpecified) {
+      // We've reached the end of the file and we didn't know the total size
+      // before. Update the total size so Read()s past the end of the file will
+      // fail like they would if we had known the file size at the beginning.
+      total_bytes_ = reader_->Tell();
+      if (total_bytes_ != kPositionNotSpecified)
+        host_->SetTotalBytes(total_bytes_);
+    }
+
     ReadOperation::Run(std::move(read_op_), bytes_read);
   } else {
     reader_->Wait(1, base::Bind(&MultibufferDataSource::ReadTask,
                                 weak_factory_.GetWeakPtr()));
     UpdateLoadingState(false);
   }
 }
 
 void MultibufferDataSource::StopInternal_Locked() {
   lock_.AssertAcquired();
@@ skipping 172 matching lines @@
   reader_->SetPinRange(back_buffer, kMaxBufferPreload + kPreloadHighExtra);
 
   if (preload_ == METADATA) {
     reader_->SetPreload(0, 0);
   } else {
     reader_->SetPreload(preload_high, preload);
   }
 }
 
 }  // namespace media