Implement Skia pipelines for OpenGL and Vulkan:
base SkiaPipeline, SkiaOpenGLPipeline and SkiaVulkanPipeline.
Write unit tests for SkiaPipeline.
Test: Built and run manually on angler-eng.
Change-Id: Ie02583426cb3547541ad9bf91700602a6163ff58
Also adds logic to clip temporary layers to viewport both for
efficiency and to allow large ones (such as the fallback case) to fit
in max texture size.
Change-Id: Iee51495220f5ca1dc7e6f5fd3615db2e896efd74
