From vkGetPipelineCacheData(3) Manual Page:

If pDataSize is less than the maximum size that can be retrieved by
the pipeline cache, at most pDataSize bytes will be written to
pData, and vkGetPipelineCacheData will return VK_INCOMPLETE. Any
data written to pData is valid and can be provided as the
pInitialData member of the VkPipelineCacheCreateInfo structure
passed to vkCreatePipelineCache.

Bug: angleproject:3988
Test: CQ, CtsOpenGLTestCases
Change-Id: I34589ee3c9e27839a9cd0168b4a2186f4cbb255e
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1854680
Commit-Queue: Tim Van Patten <timvp@google.com>
Reviewed-by: Tobin Ehlis <tobine@google.com>