Always initialize |m_totalWidth| in HarfBuzzShaper::shape.

R=leviw@chromium.org
BUG=476647

Review URL: https://codereview.chromium.org/1108663003

git-svn-id: svn://svn.chromium.org/blink/trunk@194541 bbb929c8-8fbe-4397-9dbb-9b2b20218538
static const uint16_t* toUint16(const UChar* src)
{
    static_assert(sizeof(UChar) == sizeof(uint16_t), "UChar should be the same size as uint16_t");
    return reinterpret_cast<const uint16_t*>(src);
}

static const uint16_t* toUint16(const UChar* src)
{
    static_assert(sizeof(UChar) == sizeof(uint16_t), "UChar should be the same size as uint16_t");
    return reinterpret_cast<const uint16_t*>(src);
}
