Remove optimization-blocking code.

cc/tiles/gpu_image_decode_controller.cc

Index: cc/tiles/gpu_image_decode_controller.cc
diff --git a/cc/tiles/gpu_image_decode_controller.cc b/cc/tiles/gpu_image_decode_controller.cc
index ea60fb0e28e3d778e311245c44af19968e5299d0..882346ef57650d665df14e26927d54cd4108115a 100644
--- a/cc/tiles/gpu_image_decode_controller.cc
+++ b/cc/tiles/gpu_image_decode_controller.cc
@@ -943,10 +943,8 @@ void GpuImageDecodeController::DecodeImageIfNecessary(
   {
     base::AutoUnlock unlock(lock_);
 
-    size_t image_data_size = image_data->size;
-    base::debug::Alias(&image_data_size);
     backing_memory = base::DiscardableMemoryAllocator::GetInstance()
-                         ->AllocateLockedDiscardableMemory(image_data_size);
+                         ->AllocateLockedDiscardableMemory(image_data->size);
 
     switch (image_data->mode) {
       case DecodedDataMode::CPU: {