Add checked_cast to size_t conversion in multibuffer_data_source.cc

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"
 #include "base/location.h"
 #include "base/macros.h"
+#include "base/numerics/safe_conversions.h"
 #include "base/single_thread_task_runner.h"
 #include "media/base/media_log.h"
 #include "media/blink/buffered_data_source_host_impl.h"
 #include "media/blink/multibuffer_reader.h"
 #include "net/base/net_errors.h"
 
 using blink::WebFrame;
 
 namespace {
 
@@ skipping 305 matching lines @@
   if (reader_ && (always_cancel || (preload_ == METADATA &&
                                     !media_has_played_ && !IsStreaming()))) {
     cancel_on_defer_ = true;
     if (!loading_)
       reader_.reset(nullptr);
   }
 }
 
 int64_t MultibufferDataSource::GetMemoryUsage() const {
   // TODO(hubbe): Make more accurate when url_data_ is shared.
-  return url_data_->CachedSize()
+  return base::checked_cast<int64_t>(url_data_->CachedSize())

[brucedawson, 2017/02/02 22:22:52]

Why do we need a checked cast for converting to a larger size? The cast makes
sense, I'm only curious about why a checked_cast was felt to be necessary.

But, checked_cast is probably smart enough to be free in this case so it doesn't
really matter.

[jrummell, 2017/02/03 01:35:40]

My understanding is that on some systems size_t is 64 bits, so a simple
conversion is bad. I thought Chromium encouraged use of the helpers, as past
CL's have had comments that I should use them.

          << url_data_->multibuffer()->block_size_shift();
 }
 
 GURL MultibufferDataSource::GetUrlAfterRedirects() const {
   return url_data_->url();
 }
 
 void MultibufferDataSource::Read(int64_t position,
                                  int size,
                                  uint8_t* data,
@@ skipping 284 matching lines @@
   reader_->SetPinRange(pin_backward, pin_forward);
 
   if (preload_ == METADATA) {
     reader_->SetPreload(0, 0);
   } else {
     reader_->SetPreload(preload_high, preload);
   }
 }
 
 }  // namespace media