If SpanSet.init() is called several times in a row with different
values, it is possible to change "numberOfSpans" in a way that
will prevent SpanSet.recycle() from nulling out all the spans.
This can lead to memory leaks of large objects through spans
references. User @piwai reported this leak:
com.squareup.marketfont.MarketSpan
`-[1] of array android.text.style.CharacterStyle[]
`-spans of object android.text.SpanSet
`-mCharacterStyleSpanSet of object android.text.TextLine
`-[1] of array android.text.TextLine[]
`-sCached of class android.text.TextLine
The MarketSpan instance is kept alive through a recycled TextLine
which itself contains a SpanSet.
Change-Id: Idfb2233ca16895dbe735c312662eaf0b4a2ecd65
b3a9bc038d