Battery Status API: add UMA logging for Mac.

content/browser/battery_status/battery_status_manager_mac.cc

Index: content/browser/battery_status/battery_status_manager_mac.cc
diff --git a/content/browser/battery_status/battery_status_manager_mac.cc b/content/browser/battery_status/battery_status_manager_mac.cc
index 8d6f35b3166d608ab9a2f7c7dd21e3a072304a3b..5da151a4ab0873766fb176007e1ce12604c2be9f 100644
--- a/content/browser/battery_status/battery_status_manager_mac.cc
+++ b/content/browser/battery_status/battery_status_manager_mac.cc
@@ -11,6 +11,7 @@
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/memory/ref_counted.h"
+#include "base/metrics/histogram.h"
 #include "base/time/time.h"
 #include "content/public/browser/browser_thread.h"
 #include "third_party/WebKit/public/platform/WebBatteryStatus.h"
@@ -52,6 +53,11 @@ bool CFStringsAreEqual(CFStringRef string1, CFStringRef string2) {
   return CFStringCompare(string1, string2, 0) == kCFCompareEqualTo;
 }
 
+void UpdateNumberBatteriesHistogram(int count) {
+  UMA_HISTOGRAM_CUSTOM_COUNTS(
+      "BatteryStatus.NumberBatteriesMac", count, 1, 5, 6);
+}
+
 void FetchBatteryStatus(CFDictionaryRef description,
                         blink::WebBatteryStatus& status) {
   CFStringRef current_state =
@@ -116,7 +122,7 @@ void OnBatteryStatusChanged(const BatteryCallback& callback) {
       IOPSCopyPowerSourcesList(info));
   CFIndex count = CFArrayGetCount(power_sources_list);
 
-  bool internal_source_found = false;
+  int num_internal_sources = 0;
 
   for (CFIndex i = 0; i < count; ++i) {
     CFDictionaryRef description = IOPSGetPowerSourceDescription(info,
@@ -138,12 +144,13 @@ void OnBatteryStatusChanged(const BatteryCallback& callback) {
       // TODO(timvolodine): implement the case when there are multiple internal
       // sources, e.g. when multiple batteries are present. Currently this will
       // fail a DCHECK.
-      DCHECK(!internal_source_found);
+      DCHECK(num_internal_sources == 0);
       FetchBatteryStatus(description, status);
-      internal_source_found = true;
+      num_internal_sources++;
     }
   }
 
+  UpdateNumberBatteriesHistogram(num_internal_sources);
   callback.Run(status);
 }