Reduce memory consumption for text visual with styles and emoji

Reduce memory consumption for text visual with styles and emoji

Measured using memps on target by creating 500 TextLabels, and memory
is reduced by 60% in the best case and by 25% in the worst case.

For example:

TextLabel with single color text and styles:

Before applying this patch:

S(CODE)  S(DATA)  P(CODE)  P(DATA)     PEAK      PSS       3D
  12996      236       20   275620   289148   278088   270824

After applying this patch:

S(CODE)  S(DATA)  P(CODE)  P(DATA)     PEAK      PSS       3D
  13204      236       16   126852   140308   129395   114728

TextLabel with multiple text colors (by enabling markup):

Before applying this patch:

S(CODE)  S(DATA)  P(CODE)  P(DATA)     PEAK      PSS       3D
  13204      236       20   275512   289064   278840   270824

After applying this patch:

S(CODE)  S(DATA)  P(CODE)  P(DATA)     PEAK      PSS       3D
  13204      236       16    99388   112844   102713    90696

Change-Id: I533122b647678dc9888a1f4b94efd59336e2bfdb