gpu: Reuse transfer buffers more aggresively

gpu/command_buffer/client/mapped_memory.h

Index: gpu/command_buffer/client/mapped_memory.h
diff --git a/gpu/command_buffer/client/mapped_memory.h b/gpu/command_buffer/client/mapped_memory.h
index b8f3129eb4a3cddf452e9fabe30ec62a1af12eda..a0f810c6c8c245c820e3019230254356f83da8bd 100644
--- a/gpu/command_buffer/client/mapped_memory.h
+++ b/gpu/command_buffer/client/mapped_memory.h
@@ -18,7 +18,10 @@ class CommandBufferHelper;
 // Manages a shared memory segment.
 class GPU_EXPORT MemoryChunk {
  public:
-  MemoryChunk(int32 shm_id, gpu::Buffer shm, CommandBufferHelper* helper);
+  MemoryChunk(int32 shm_id,
+              gpu::Buffer shm,
+              bool aggressive_reuse,
+              CommandBufferHelper* helper);
 
   // Gets the size of the largest free block that is available without waiting.
   unsigned int GetLargestFreeSizeWithoutWaiting() {
@@ -107,6 +110,19 @@ class GPU_EXPORT MemoryChunk {
   DISALLOW_COPY_AND_ASSIGN(MemoryChunk);
 };
 
+// Configure MappedMemoryManager
+struct GPU_EXPORT MappedMemoryManagerSettings {
+  // |unused_memory_reclaim_limit|: When exceeded this causes pending memory
+  // to be reclaimed before allocating more memory.
+  size_t unused_memory_reclaim_limit;
+
+  // |aggressive_reuse|: When set to true, the memory manager will reuse a
+  // block marked either as FREE or FREE_PENDING_TOKEN. This setting is only
+  // allowed if the user can guarantee that all parts are done using a block
+  // that was free:ed by the client.
+  bool aggressive_reuse;
+};
+
 // Manages MemoryChunks.
 class GPU_EXPORT MappedMemoryManager {
  public:
@@ -114,10 +130,8 @@ class GPU_EXPORT MappedMemoryManager {
     kNoLimit = 0,
   };
 
-  // |unused_memory_reclaim_limit|: When exceeded this causes pending memory
-  // to be reclaimed before allocating more memory.
   MappedMemoryManager(CommandBufferHelper* helper,
-                      size_t unused_memory_reclaim_limit);
+                      MappedMemoryManagerSettings settings);
 
   ~MappedMemoryManager();
 
@@ -175,6 +189,7 @@ class GPU_EXPORT MappedMemoryManager {
   MemoryChunkVector chunks_;
   size_t allocated_memory_;
   size_t max_free_bytes_;
+  bool aggressive_reuse_;
 
   DISALLOW_COPY_AND_ASSIGN(MappedMemoryManager);
 };