Fix http://codereview.chromium.org/6869009 to ignore an existing object exactly once and land the...

Fix http://codereview.chromium.org/6869009 to ignore an existing object exactly once and land the CL again:

Introduce the ANNOTATE_LEAKING_OBJECT_PTR annotation that can be used to mark
heap allocated objects as intentionally leaked ones.
Annotate the histograms produced by {Histogram,BooleanHistogram,LinearHistogram,CustomHistogram}::FactoryGet(), as leaked.

Rename StatsHistogram::StatsHistogramFactoryGet to StatsHistogram::FactoryGet, annotate the result as leaky, update the suppressions.

BUG=79322
TBR=jar
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=86990