Backports https://github.com/WordPress/gutenberg/pull/46074 into the core.
render_layout_support_flag is run per block, and inside we called get_global_settings three times. get_global_settings calls get_merged_data, which is costly. render_layout_support_flag is a filter called during the block render. When the blocks start rendering, there is no expectation that the theme.json settings change during the block render, so the settings and their derived information should all be static information of this function.
This simple change removes 3*NUMBER_OF_BLOCKS calls of get_merged_data to just one call.
Props oandregal, aristath, felixarntz, tellthemachines, andrewserong, aaronrobertshaw, aaronrobertshaw.
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