9d7ba5629a
Part of https://github.com/flutter/flutter/issues/138236 Creating the first VkRenderPass takes 6ms on a Pixel 7. In the previous PR I attempted to use the Impeller HAL API, but this caused more problems than it solved - breaking mocks and also leading to odd behavior I think may be due to threading issues when submitting the bootstrap cmd buffer. It seems like all we need to do to trigger the shader compilation is create the render pass, so add a ContextVK override that creates and throws it away, without beginning the render pass, creating a cmd buffer, or doing any extra work.