WebKit: out-of-bounds read in WebCore::RenderText::localCaretRect(CVE-2017-13785)

There is an out-of-bounds read security vulnerability in WebKit. The vulnerability was confirmed on ASan build of WebKit nightly. ASan log: ================================================================= ==30388==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6030000f5de6 at pc...