SimpleFontData is 5632 bytes big, mostly because of the 255 * sizeof(FloatRect) cache, which is only used in the complex code path. We can shrink it by allocating this cache lazily. It's 1536 bytes after this change.
Created attachment 56189 [details] Patch
Comment on attachment 56189 [details] Patch r=me
<rdar://problem/7990089>
http://trac.webkit.org/changeset/59577
http://trac.webkit.org/changeset/59577 might have broken GTK Linux 64-bit Debug
I'm not sure how this could be possible, but the buildbot says this change caused a Gtk layout test to crash: http://build.webkit.org/results/GTK%20Linux%2064-bit%20Debug/r59577%20(5945)/fast/workers/storage/execute-sql-args-worker-stderr.txt ASSERTION FAILED: !protectedObjectCount() (../../JavaScriptCore/runtime/Collector.cpp:323 void JSC::Heap::freeBlocks()) It's crashed on every build since this was checked in. It's possible this was an earlier regression which was not noticed earlier due to Gtk build system dependency tracking problems.
Nevermind, looks like this test has been flaky for a while: http://build.webkit.org/results/GTK%20Linux%2064-bit%20Debug/r59574%20(5941)/results.html
Filed the false positive as bug 39183.