Cap the memory usage in FFMpegDemuxer.

media/base/decoder_buffer_queue.cc

Index: media/base/decoder_buffer_queue.cc
diff --git a/media/base/decoder_buffer_queue.cc b/media/base/decoder_buffer_queue.cc
index d0486cbf93965932bcbf7108f24cd947f79c499c..26ba9f4e69ba7b5071599dbf1c9019f22d366df9 100644
--- a/media/base/decoder_buffer_queue.cc
+++ b/media/base/decoder_buffer_queue.cc
@@ -5,13 +5,15 @@
 #include "media/base/decoder_buffer_queue.h"
 
 #include "base/logging.h"
+#include "base/numerics/safe_conversions.h"
 #include "media/base/buffers.h"
 #include "media/base/decoder_buffer.h"
 
 namespace media {
 
 DecoderBufferQueue::DecoderBufferQueue()
-    : earliest_valid_timestamp_(kNoTimestamp()) {
+    : earliest_valid_timestamp_(kNoTimestamp()),
+      data_size_(0) {
 }
 
 DecoderBufferQueue::~DecoderBufferQueue() {}
@@ -21,6 +23,10 @@ void DecoderBufferQueue::Push(const scoped_refptr<DecoderBuffer>& buffer) {
 
   queue_.push_back(buffer);
 
+  // TODO(damienv): Remove the cast here and in every place in this file
+  // when DecoderBuffer::data_size is modified to return a size_t.
+  data_size_ += base::checked_cast<size_t, int>(buffer->data_size());
+
   // TODO(scherkus): FFmpeg returns some packets with no timestamp after
   // seeking. Fix and turn this into CHECK(). See http://crbug.com/162192
   if (buffer->timestamp() == kNoTimestamp()) {
@@ -49,6 +55,11 @@ scoped_refptr<DecoderBuffer> DecoderBufferQueue::Pop() {
   scoped_refptr<DecoderBuffer> buffer = queue_.front();
   queue_.pop_front();
 
+  size_t buffer_data_size =
+      base::checked_cast<size_t, int>(buffer->data_size());
+  DCHECK_LE(buffer_data_size, data_size_);
+  data_size_ -= buffer_data_size;
+
   if (!in_order_queue_.empty() &&
       in_order_queue_.front().get() == buffer.get()) {
     in_order_queue_.pop_front();
@@ -59,6 +70,7 @@ scoped_refptr<DecoderBuffer> DecoderBufferQueue::Pop() {
 
 void DecoderBufferQueue::Clear() {
   queue_.clear();
+  data_size_ = 0;
   in_order_queue_.clear();
   earliest_valid_timestamp_ = kNoTimestamp();
 }