[4.0] Reduce memory consumption for text visual with styles and emoji

[4.0] 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