gpu: Allow BufferData size=0 for pixel transfer buffer objects.

gpu/command_buffer/client/buffer_tracker_unittest.cc

 // Copyright (c) 2012 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.
 
 // Tests for the BufferTracker.
 
 #include "gpu/command_buffer/client/buffer_tracker.h"
 
 #include <GLES2/gl2ext.h>
 #include "base/memory/scoped_ptr.h"
@@ skipping 52 matching lines @@
   EXPECT_TRUE(buffer_tracker_->GetBuffer(kId2) == NULL);
   // Check we can delete the buffer.
   buffer_tracker_->RemoveBuffer(kId1);
   // Check shared memory was freed.
   mapped_memory_->FreeUnused();
   EXPECT_EQ(0lu, mapped_memory_->num_chunks());
   // Check we get nothing for a non-existent buffer.
   EXPECT_TRUE(buffer_tracker_->GetBuffer(kId1) == NULL);
 }
 
+TEST_F(BufferTrackerTest, ZeroSize) {
+  const GLuint kId = 123;
+
+  // Check we can create a Buffer with zero size.
+  BufferTracker::Buffer* buffer = buffer_tracker_->CreateBuffer(kId, 0);
+  ASSERT_TRUE(buffer != NULL);
+  // Check mapped memory address.
+  EXPECT_TRUE(buffer->address() == NULL);
+  // Check no shared memory was allocated.
+  EXPECT_EQ(0lu, mapped_memory_->num_chunks());
+  // Check we can delete the buffer.
+  buffer_tracker_->RemoveBuffer(kId);
+}
+
 }  // namespace gles2
 }  // namespace gpu