Add support for sparse histograms to WebKitPlatformSupportImpl

webkit/glue/webkitplatformsupport_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "webkit/glue/webkitplatformsupport_impl.h"
 
 #include <math.h>
 
 #include <vector>
 
 #include "base/allocator/allocator_extension.h"
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
 #include "base/message_loop.h"
 #include "base/metrics/histogram.h"
+#include "base/metrics/sparse_histogram.h"
 #include "base/metrics/stats_counters.h"
 #include "base/platform_file.h"
 #include "base/process_util.h"
 #include "base/rand_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/synchronization/lock.h"
 #include "base/sys_info.h"
 #include "base/time/time.h"
@@ skipping 408 matching lines @@
     const char* name, int sample, int boundary_value) {
   // Copied from histogram macro, but without the static variable caching
   // the histogram because name is dynamic.
   base::HistogramBase* counter =
       base::LinearHistogram::FactoryGet(name, 1, boundary_value,
           boundary_value + 1, base::HistogramBase::kUmaTargetedHistogramFlag);
   DCHECK_EQ(name, counter->histogram_name());
   counter->Add(sample);
 }
 
+void WebKitPlatformSupportImpl::histogramSparse(const char* name, int sample) {
+  UMA_HISTOGRAM_SPARSE_SLOWLY(name, sample);

[jar (doing other things), 2013/07/19 17:55:28]

nit: This works perfectly... but it scared me, since you can't use the UMA
histogram macros (usually) when the name is variable.  Can you add the comment:

// For sparse histograms, we can use the macro, as it does not incorporate a
static.



FWIW: We should not use a macro definition for this, and the sparse_histogram.h
file should instead define a *function* in this case.  I didn't see the review,
or I would have pointed out that we prefer functions, and only use macros when
we are forced to.  Oh well.

[ajuma, 2013/07/19 18:37:21]

Done.

+}
+
 const unsigned char* WebKitPlatformSupportImpl::getTraceCategoryEnabledFlag(
     const char* category_group) {
   return TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(category_group);
 }
 
 long* WebKitPlatformSupportImpl::getTraceSamplingState(
     const unsigned thread_bucket) {
   // Not supported in split-dll build. http://crbug.com/237249
 #if !defined(CHROME_SPLIT_DLL)
   switch (thread_bucket) {
@@ skipping 428 matching lines @@
   if (--shared_timer_suspended_ == 0 &&
       (!shared_timer_.IsRunning() ||
        shared_timer_fire_time_was_set_while_suspended_)) {
     shared_timer_fire_time_was_set_while_suspended_ = false;
     setSharedTimerFireInterval(
         shared_timer_fire_time_ - monotonicallyIncreasingTime());
   }
 }
 
 }  // namespace webkit_glue