Activate reduced shader mode in SkiaGlRenderEngine

Test: build with https://skia-review.googlesource.com/c/skia/+/416299 and use perfetto to count
shaders compiled in cache warming step, expect 51, not 83.

Bug: b/187535297

Change-Id: Iffd827ba8fbb6f6ec4fa961f11eb920b1a26bcc2