Bug 723846 - Part 1: add FlagHistogram to ipc. r=taras

ipc/chromium/src/base/histogram.cc

@@ -916,6 +916,52 @@ BooleanHistogram::BooleanHistogram(const std::string& name)
     : LinearHistogram(name, 1, 2, 3) {
 }
 
+//------------------------------------------------------------------------------
+// FlagHistogram:
+//------------------------------------------------------------------------------
+
+Histogram *
+FlagHistogram::FactoryGet(const std::string &name, Flags flags)
+{
+  Histogram *h(nsnull);
+
+  if (!StatisticsRecorder::FindHistogram(name, &h)) {
+    // To avoid racy destruction at shutdown, the following will be leaked.
+    FlagHistogram *fh = new FlagHistogram(name);
+    fh->InitializeBucketRange();
+    fh->SetFlags(flags);
+    size_t zero_index = fh->BucketIndex(0);
+    fh->Histogram::Accumulate(1, 1, zero_index);
+    h = StatisticsRecorder::RegisterOrDeleteDuplicate(fh);
+  }
+
+  return h;
+}
+
+FlagHistogram::FlagHistogram(const std::string &name)
+  : BooleanHistogram(name), mSwitched(false) {
+}
+
+Histogram::ClassType
+FlagHistogram::histogram_type() const
+{
+  return FLAG_HISTOGRAM;
+}
+
+void
+FlagHistogram::Accumulate(Sample value, Count count, size_t index)
+{
+  if (mSwitched) {
+    return;
+  }
+
+  mSwitched = true;
+  DCHECK_EQ(value, 1);
+  Histogram::Accumulate(value, 1, index);
+  size_t zero_index = BucketIndex(0);
+  Histogram::Accumulate(1, -1, zero_index);
+}
+
 //------------------------------------------------------------------------------
 // CustomHistogram:
 //------------------------------------------------------------------------------

ipc/chromium/src/base/histogram.h

@@ -276,6 +276,7 @@ class Histogram {
     HISTOGRAM,
     LINEAR_HISTOGRAM,
     BOOLEAN_HISTOGRAM,
+    FLAG_HISTOGRAM,
     CUSTOM_HISTOGRAM,
     NOT_VALID_IN_RENDERER
   };
@@ -642,7 +643,7 @@ class BooleanHistogram : public LinearHistogram {
 
   virtual void AddBoolean(bool value);
 
- private:
+ protected:
   explicit BooleanHistogram(const std::string& name);
 
   DISALLOW_COPY_AND_ASSIGN(BooleanHistogram);
@@ -650,6 +651,25 @@ class BooleanHistogram : public LinearHistogram {
 
 //------------------------------------------------------------------------------
 
+// FlagHistogram is like boolean histogram, but only allows a single off/on value.
+class FlagHistogram : public BooleanHistogram
+{
+public:
+  static Histogram *FactoryGet(const std::string &name, Flags flags);
+
+  virtual ClassType histogram_type() const;
+
+  virtual void Accumulate(Sample value, Count count, size_t index);
+
+private:
+  explicit FlagHistogram(const std::string &name);
+  bool mSwitched;
+
+  DISALLOW_COPY_AND_ASSIGN(FlagHistogram);
+};
+
+//------------------------------------------------------------------------------
+
 // CustomHistogram is a histogram for a set of custom integers.
 class CustomHistogram : public Histogram {
  public: