Script streaming: UTF-8 handling fix.

Script streaming: UTF-8 handling fix.

The problem was that there can be several multi-byte UTF-8 characters near the
splitting point of the data chunks, and the code didn't handle it properly.

This was also the source of crbug.com/417891 - I thought the crash can only
happen when V8 is passed invalid UTF-8 data, but it can also happen in the
abovementioned case. After the fix, we handle the valid UTF-8 case and also
guard against invalid UTF-8 data.

R=yangguo@chromium.org
BUG=chromium:417891
LOG=N

Committed: https://code.google.com/p/v8/source/detail?r=24547

[marja, 2014-10-13 08:31:48]

yangguo, ptal

[marja, 2014-10-13 08:31:51]

yangguo, ptal

[Yang, 2014-10-13 08:34:53]

On 2014/10/13 08:31:51, marja (ooo until 13th Oct) wrote:
> yangguo, ptal

lgtm.

[marja, 2014-10-13 09:02:05]

Committed patchset #1 (id:1) manually as 24547 (presubmit successful).