Add ImmutableMap methods 'manualRetain()', 'manualRelease()', and 'getRootWithoutRetain()' to help more aggressively reclaim memory in the static analyzer.
Add ImmutableMap methods 'manualRetain()', 'manualRelease()', and 'getRootWithoutRetain()' to help more aggressively reclaim memory in the static analyzer.

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@126011 91177308-0d34-0410-b5e6-96231b3b80d8

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