Fix Bug in RingBuffer

TEST=unit test
BUG=42859 

Review URL: http://codereview.chromium.org/1806003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@46017 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 5 insertions, 1 deletions

diff --git a/gpu/command_buffer/client/ring_buffer.cc b/gpu/command_buffer/client/ring_buffer.cc
index 678110a..89da7fe 100644
--- a/gpu/command_buffer/client/ring_buffer.cc
+++ b/gpu/command_buffer/client/ring_buffer.cc
@@ -40,11 +40,13 @@ void RingBuffer::FreeOldestBlock() {
     in_use_offset_ = 0;
     free_offset_ = 0;
   }
-  blocks_.pop_back();
+  blocks_.pop_front();
 }
 
 RingBuffer::Offset RingBuffer::Alloc(unsigned int size) {
   DCHECK_LE(size, size_) << "attempt to allocate more than maximum memory";
+  DCHECK(blocks_.empty() || blocks_.back().valid)
+      << "Attempt to alloc another block before freeing the previous.";
   // Similarly to malloc, an allocation of 0 allocates at least 1 byte, to
   // return different pointers every time.
   if (size == 0) size = 1;
@@ -82,6 +84,8 @@ void RingBuffer::FreePendingToken(RingBuffer::Offset offset,
 }
 
 unsigned int RingBuffer::GetLargestFreeSizeNoWaiting() {
+  // TODO(gman): Should check what the current token is and free up to that
+  //    point.
   if (free_offset_ == in_use_offset_) {
     if (blocks_.empty()) {
       // The entire buffer is free.