MacViews: Only use context for text shape when using RTL languages

The call to hb_buffer_add_utf16 will read up to 5 characters adjacent
to the specified range. This context is only used in the function
arabic_joining.

We can get much better caching if we don't include this context in our
keys. Arabic is an RTL language, so we can omit this context in the key
for all non-RTL languages.

Bug: 860612, 862773
Change-Id: Icc11059886ab835032141ad25b966d358f7177b3
Reviewed-on: https://chromium-review.googlesource.com/1135723
Commit-Queue: ccameron <[email protected]>
Reviewed-by: Sidney San Martín <[email protected]>
Cr-Commit-Position: refs/heads/master@{#574834}
1 file changed