Introduce FontCache content scaling
FontPlatformData stored in FontCache has size-independent backing font
data on non-Mac platform, and can be safely reused for different font
sizes by scaling.
This CL modifies FontCache to reuse a FontPlatformData to different size
of font, so that Blink's layout phase requires smaller number of expensive
synchronous IPCs.
This reduces the first layout time of text-heavy CJK sites on Linux.
E.g. reduces layout time of http://b.hatena.ne. jp/ from 740ms to 515ms,
and https://ja-jp.facebook.com/legal/terms from 453ms to 428ms.
BUG=608650
Review-Url: https://codereview.chromium.org/1962263002
Cr-Commit-Position: refs/heads/master@{#395022}
10 files changed
