Introduce PremeasuredText

By measuring the character widths beforehand, we can save at least 40%
of the StaticLayout construction time which typically happens on UI
thread.
Also verified this doesn't cause performance regression for not
premeasured text.

Raw performance score (Not premeasured -> premeasured, median, N=100)

No Style,   Greedy, Hyphenation OFF:  7,812,975 ->    503,245 (-93.6%)
No Style, Balanced, Hyphenation OFF:  7,843,254 ->    396,892 (-95.0%)

No Style,   Greedy, Hyphenation ON : 19,134,214 -> 11,658,928 (-39.1%)
No Style, Balanced, Hyphenation ON : 19,348,062 -> 11,634,942 (-39.9%)

Styled,     Greedy, Hyphenation OFF: 14,353,673 ->    572,840 (-96.0%)

Raw performance score (w/o patch -> w/ patch, median, N=100):

No Style,   Greedy, Hyphenation OFF:  7,732,894 ->  7,812,975 (+1.04%)
No Style, Balanced, Hyphenation OFF:  7,884,510 ->  7,843,254 (-0.52%)

No Style,   Greedy, Hyphenation ON : 18,986,958 -> 19,134,214 (+0.78%)
No Style, Balanced, Hyphenation ON : 19,232,791 -> 19,348,062 (+0.60%)

Styled,     Greedy, Hyphenation OFF: 14,319,690 -> 14,353,673 (+0.24%)

Bug: 67504091
Test: bit CtsTextTestCases:*
Test: bit CtsGraphicsTestCases:*
Test: bit CtsWidgetTestCases:*
Test: FrameworksCoreTests:android.text.MeasuredTextTest
Change-Id: I0b46f04b42cc012606a9c722eca0d51147a0dcc7