Avoid an overflow in harfbuzz-myanmar.c

Adds a guard to prevent invalid assignment.

BUG=108006

TEST=manually with ASAN.


Review URL: http://codereview.chromium.org/8997001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@115859 0039d316-1c4b-4281-b951-d872f2087c98
getMyanmarCharClass (HB_UChar16 ch)
{
    if (ch == Mymr_C_SIGN_ZWJ)
        return Mymr_CC_ZERO_WIDTH_J_MARK;

    if (ch == Mymr_C_SIGN_ZWNJ)
        return Mymr_CC_ZERO_WIDTH_NJ_MARK;

    if (ch < 0x1000 || ch > 0x105f)
        return Mymr_CC_RESERVED;

    return mymrCharClasses[ch - 0x1000];
}

getMyanmarCharClass (HB_UChar16 ch)
{
    if (ch == Mymr_C_SIGN_ZWJ)
        return Mymr_CC_ZERO_WIDTH_J_MARK;

    if (ch == Mymr_C_SIGN_ZWNJ)
        return Mymr_CC_ZERO_WIDTH_NJ_MARK;

    if (ch < 0x1000 || ch > 0x105f)
        return Mymr_CC_RESERVED;

    return mymrCharClasses[ch - 0x1000];
}
