Shorthand support for SMIL
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This is a PR for https://bugzilla.mozilla.org/show_bug.cgi?id=1358966
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We convert ComputedOperation::{Accumulate, Interpolate}Matrix into gecko type
not on the main thread, so we cannot use nsCSSValueList_heap (which is not
thread safe so we cannot create it and destroy it on different threads).
Therefore, we use nsCSSValueSharedList to represent the cloned
from_list/to_list. In this patch, we also implement the reversing way,
i.e. Convert eCSSKeyword_{accumulate, interpolate}matrix into
{Accumulate, Interpolate}Matrix.
MallocSizeOf is similar to the existing HeapSizeOf trait from the
heapsize crate. The only difference is that MallocSizeOf's
malloc_size_of_children() function takes an additional MallocSizeOfFn
argument, which is used to measure heap blocks. This extra argument
makes MallocSizeOf match how Gecko's memory measurements work, and is
required for Stylo to integrate with DMD.
The patch also introduces a second trait, MallocSizeOfWithGuard, which
is much the same as MallocSizeOf, but with a |guard| argument for the
global style lock.
Finally, the patch uses the new traits to measure a small amount of
Stylo's memory usage.
Stylo: Deep clone ServoStyleSheets.
MozReview-Commit-ID: 6hYIcOa86Y
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https://bugzilla.mozilla.org/show_bug.cgi?id=1339629https://reviewboard.mozilla.org/r/135314/
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