Inline performance-critical methods on SkAlphaRuns

Inline performance-critical methods on SkAlphaRuns.

Clang needs to be forced to inline add, so we do that.

GCC on desktop
              bench conf time        old        new       diff    diffP
draw_coverage_false 8888 c        236.08     212.01     +24.07   +10.2%
 draw_coverage_true 8888 c        125.67     104.49     +21.18   +16.9%


GCC on N5
              bench conf time        old        new       diff    diffP
draw_coverage_false 8888 c        566.33     529.96     +36.37    +6.4%
 draw_coverage_true 8888 c        315.39     293.85     +21.54    +6.8%


Clang on desktop
              bench conf time        old        new       diff    diffP
draw_coverage_false 8888 c        337.37     330.63      +6.74    +2.0%
 draw_coverage_true 8888 c        126.87     119.32      +7.55    +6.0%

BUG=
R=reed@google.com

Committed: https://code.google.com/p/skia/source/detail?r=12370

[mtklein, 2013-11-22 21:24:00]

Sadly, this is ~100% of the speedup I'm seeing on my other branch.

[reed1, 2013-11-22 21:25:09]

lgtm

[mtklein, 2013-11-22 21:25:58]

Committed patchset #1 manually as r12370 (presubmit successful).