Add memory limits struct to in-process context

Add SharedMemoryLimits struct to in-process command buffer
context. Pick a reasonable value for the reclaim limit for
synchronous compositor

BUG=402086

Review URL: https://codereview.chromium.org/455083002

git-svn-id: http://src.chromium.org/svn/trunk/src/gpu@290764 4ff67af0-8c30-449e-8e8b-ad334ec8d88c