Return a NULL histogram pointer on construction error

base/metrics/histogram.cc

Index: base/metrics/histogram.cc
diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index fbe66d05d29fd3c2896f8499dd1dc07d9793d095..2d8a7c9d33844156d8184747d5a263b2a37fc133 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -76,6 +76,23 @@ bool ValidateRangeChecksum(const HistogramBase& histogram,
   return casted_histogram.bucket_ranges()->checksum() == range_checksum;
 }
 
+// DummyHistogram is an object that overrides Histogram's Add* functions
+// to provide no functionality. This can be returned in the case of mismatched
+// construction arguments to any of the other Histograms' FactoryGet calls.
+class DummyHistogram : public Histogram {
+ public:
+  virtual void Add(Sample value) OVERRIDE {}
+  virtual void AddSamples(const HistogramSamples& samples) OVERRIDE {}
+  virtual bool AddSamplesFromPickle(PickleIterator* iter) OVERRIDE {
+    return false;
+  }
+
+  DummyHistogram() : Histogram("Dummy", 0, 1, NULL) {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DummyHistogram);
+};
+
 }  // namespace
 
 typedef HistogramBase::Count Count;
@@ -88,7 +105,8 @@ HistogramBase* Histogram::FactoryGet(const string& name,
                                      Sample minimum,
                                      Sample maximum,
                                      size_t bucket_count,
-                                     int32 flags) {
+                                     int32 flags,
+                                     int32 construction_behavior) {
   bool valid_arguments =
       InspectConstructionArguments(name, &minimum, &maximum, &bucket_count);
   DCHECK(valid_arguments);
@@ -110,7 +128,21 @@ HistogramBase* Histogram::FactoryGet(const string& name,
   }
 
   DCHECK_EQ(HISTOGRAM, histogram->GetHistogramType());
-  CHECK(histogram->HasConstructionArguments(minimum, maximum, bucket_count));
+  if (construction_behavior == kAllowBadConstruction) {
+    if (!histogram->HasConstructionArguments(minimum, maximum, bucket_count)) {
+      // The construction arguments do not match the existing histogram.  This
+      // can come about if an extension updates in the middle of a chrome run
+      // and has changed one of them.  We return a dummy object here instead of
+      // crashing so poor use of extension/Pepper APIs do not cause crashes in
+      // Chrome.
+      DLOG(ERROR) << "Histogram " << name << " has bad construction arguments";
+      DummyHistogram* tentative_histogram = new DummyHistogram;
+      histogram =
+          StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
+    }
+  } else {
+    CHECK(histogram->HasConstructionArguments(minimum, maximum, bucket_count));
+  }
   return histogram;
 }
 
@@ -118,9 +150,10 @@ HistogramBase* Histogram::FactoryTimeGet(const string& name,
                                          TimeDelta minimum,
                                          TimeDelta maximum,
                                          size_t bucket_count,
-                                         int32 flags) {
+                                         int32 flags,
+                                         int32 construction_behavior) {
   return FactoryGet(name, minimum.InMilliseconds(), maximum.InMilliseconds(),
-                    bucket_count, flags);
+                    bucket_count, flags, construction_behavior);
 }
 
 TimeTicks Histogram::DebugNow() {
@@ -517,18 +550,20 @@ HistogramBase* LinearHistogram::FactoryGet(const string& name,
                                            Sample minimum,
                                            Sample maximum,
                                            size_t bucket_count,
-                                           int32 flags) {
+                                           int32 flags,
+                                           int32 construction_behavior) {
   return FactoryGetWithRangeDescription(
-      name, minimum, maximum, bucket_count, flags, NULL);
+      name, minimum, maximum, bucket_count, flags, NULL, construction_behavior);
 }
 
 HistogramBase* LinearHistogram::FactoryTimeGet(const string& name,
                                                TimeDelta minimum,
                                                TimeDelta maximum,
                                                size_t bucket_count,
-                                               int32 flags) {
+                                               int32 flags,
+                                               int32 construction_behavior) {
   return FactoryGet(name, minimum.InMilliseconds(), maximum.InMilliseconds(),
-                    bucket_count, flags);
+                    bucket_count, flags, construction_behavior);
 }
 
 HistogramBase* LinearHistogram::FactoryGetWithRangeDescription(
@@ -537,7 +572,8 @@ HistogramBase* LinearHistogram::FactoryGetWithRangeDescription(
       Sample maximum,
       size_t bucket_count,
       int32 flags,
-      const DescriptionPair descriptions[]) {
+      const DescriptionPair descriptions[],
+      int32 construction_behavior) {
   bool valid_arguments = Histogram::InspectConstructionArguments(
       name, &minimum, &maximum, &bucket_count);
   DCHECK(valid_arguments);
@@ -567,7 +603,21 @@ HistogramBase* LinearHistogram::FactoryGetWithRangeDescription(
   }
 
   DCHECK_EQ(LINEAR_HISTOGRAM, histogram->GetHistogramType());
-  CHECK(histogram->HasConstructionArguments(minimum, maximum, bucket_count));
+  if (construction_behavior == kAllowBadConstruction) {
+    if (!histogram->HasConstructionArguments(minimum, maximum, bucket_count)) {
+      // The construction arguments do not match the existing histogram.  This
+      // can come about if an extension updates in the middle of a chrome run
+      // and has changed one of them.  We return a dummy object here instead of
+      // crashing so poor use of extension/Pepper APIs do not cause crashes in
+      // Chrome.
+      DLOG(ERROR) << "Histogram " << name << " has bad construction arguments";
+      DummyHistogram* tentative_histogram = new DummyHistogram;
+      histogram =
+          StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
+    }
+  } else {
+    CHECK(histogram->HasConstructionArguments(minimum, maximum, bucket_count));
+  }
   return histogram;
 }