MIPS: fix error with number of registers.

Some versions of compiler in debug build can't find
a register in class 'GR_REGS' while reloading 'asm'

Number of used registers is decreased in this fix.

Change-Id: I7d7b8172b8f37f1de4db3d8534a346d7a72c5065
Bugfix: Incremental decode of lossy-alpha

When remapping buffer, br->eos_ was wrongly being set to true for
certain
images.

Also, refactored the end-of-stream detection as a function.

Reported in http://crbug.com/364830

Change-Id: I716ce082ef2b505fe24246b9c14912d8e97b5d84
Merge "Bugfix: Incremental decode of lossy-alpha"