Cleanup histogram classes mixing SetFlags into FactoryGet arguments

Generic cleanup of histogram class, renaming *FactoryGet to FactoryGet,
along with reformatting.

The macros were cleaned up to use common sub-macros rather than
repeating code as much.

Removed ThreadSafeHistogram (and associated ASSET_HISTOGRAM macros)
since this class was not getting used.

I introduced UMA_HISTOGRAM_ENUMERATION to support the common use
of LinearHistograms to count various enumerated values.

I added a Flags argument to all the FactoryGet routines to help avoid 
needing to call SetFlags each time a new sample is Add()ed.  This also
simplifies the code.

This will all help prepare for a "don't histogram at all" macro setting
so that I can test the impact of the histogram macro calls on
performance (since there are now so many active histograms).

BUG=31206
r=raman.tenneti
Review URL: http://codereview.chromium.org/515033

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@35295 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 5 insertions, 8 deletions

diff --git a/base/message_loop.cc b/base/message_loop.cc
index 64913e5..9799100 100644
--- a/base/message_loop.cc
+++ b/base/message_loop.cc
@@ -265,7 +265,7 @@ void MessageLoop::PostTask_Helper(
     pending_task.delayed_run_time =
         Time::Now() + TimeDelta::FromMilliseconds(delay_ms);
   } else {
-    DCHECK(delay_ms == 0) << "delay should not be negative";
+    DCHECK_EQ(delay_ms, 0) << "delay should not be negative";
   }
 
   // Warning: Don't try to short-circuit, and handle this thread's tasks more
@@ -531,13 +531,10 @@ void MessageLoop::StartHistogrammer() {
   if (enable_histogrammer_ && !message_histogram_.get()
       && StatisticsRecorder::WasStarted()) {
     DCHECK(!thread_name_.empty());
-    message_histogram_ =
-        LinearHistogram::LinearHistogramFactoryGet(
-                            ("MsgLoop:" + thread_name_),
-                            kLeastNonZeroMessageId,
-                            kMaxMessageId,
-                            kNumberOfDistinctMessagesDisplayed);
-    message_histogram_->SetFlags(message_histogram_->kHexRangePrintingFlag);
+    message_histogram_ = LinearHistogram::FactoryGet("MsgLoop:" + thread_name_,
+        kLeastNonZeroMessageId, kMaxMessageId,
+        kNumberOfDistinctMessagesDisplayed,
+        message_histogram_->kHexRangePrintingFlag);
     message_histogram_->SetRangeDescriptions(event_descriptions_);
   }
 }