Use factory to create histograms, and refcounts to track lifetimes

This is CL patch 377028 by Raman Tenneti, with minor changes to
make the try-bots happier.

It is cleanup that better ensures lifetimes of histograms (making it harder
for users to abuse them).  

bug=16495 (repairs leak induced by the first landing)
bug=18840 (should make leaks less possible)
tbr=raman.tenneti
Review URL: http://codereview.chromium.org/462027

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@33933 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 11 insertions, 5 deletions

diff --git a/chrome/renderer/render_thread.cc b/chrome/renderer/render_thread.cc
index a4b36a6..d22f52a0 100644
--- a/chrome/renderer/render_thread.cc
+++ b/chrome/renderer/render_thread.cc
@@ -482,11 +482,17 @@ void RenderThread::SetCacheMode(bool enabled) {
 
 static void* CreateHistogram(
     const char *name, int min, int max, size_t buckets) {
-  Histogram* histogram = new Histogram(name, min, max, buckets);
-  if (histogram) {
-    histogram->SetFlags(kUmaTargetedHistogramFlag);
-  }
-  return histogram;
+  if (min <= 0)
+    min = 1;
+  scoped_refptr<Histogram> histogram =
+      Histogram::HistogramFactoryGet(name, min, max, buckets);
+  // We verify this was not being destructed by setting a novel "PlannedLeak"
+  // flag and watching out for the flag in the destructor.
+  histogram->SetFlags(kUmaTargetedHistogramFlag | kPlannedLeakFlag);
+  // We'll end up leaking these histograms, unless there is some code hiding in
+  // there to do the dec-ref.
+  histogram->AddRef();
+  return histogram.get();
 }
 
 static void AddHistogramSample(void* hist, int sample) {