Benchmark for edge extension shader effect

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Benchmark                                Time             CPU   Iterations
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BM_homescreen/SkiaGLThreaded                  1245547 ns        36726 ns        10000
BM_homescreen_edgeExtension/SkiaGLThreaded    1271118 ns        36986 ns        10000

Bug: 322036393
Test: Compare drawing a layer with and without edge extension shader
Flag: TEST_ONLY
Change-Id: Ia1dd3c6fa6bf4b5281517a3bf93c7e58ae840c70