Add GLES2Implemention::FreeUnusedSharedMemory

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 f5f3e379d3d13ad2e311310b34e9d1c243844d51..b78c29370d90e32248bccbcf23f2446a31b75536 100644
--- a/gpu/command_buffer/client/mapped_memory.h
+++ b/gpu/command_buffer/client/mapped_memory.h
@@ -90,6 +90,11 @@ class MemoryChunk {
            pointer < reinterpret_cast<const int8*>(shm_.ptr) + shm_.size;
   }
 
+  // Returns true of any memory in this chuck is in use.
+  bool InUse() {
+    return allocator_.InUse();
+  }
+
  private:
   int32 shm_id_;
   gpu::Buffer shm_;
@@ -129,6 +134,14 @@ class MappedMemoryManager {
   //   token: the token value to wait for before re-using the memory.
   void FreePendingToken(void* pointer, int32 token);
 
+  // Free Any Shared memory that is not in use.
+  void FreeUnused();
+
+  // Used for testing
+  size_t num_chunks() {
+    return chunks_.size();
+  }
+
  private:
   typedef std::vector<MemoryChunk*> MemoryChunkVector;