commit 36e0f57de3e540c00b3ab63adfc46d3a79ed9746
author Qingsi Wang <qingsi@google.com> Thu Jan 17 02:37:21 2019
committer Commit Bot <commit-bot@chromium.org> Mon Jan 21 10:44:35 2019
tree 80ce95bd4ed1877f78a341251a1cbf3f5c4b25f1
parent 4241cf5ed5d8ce0531b6e0b3933ba665e4b656f0

Replace the usage of RTC_HISTOGRAM_COMMON_BLOCK with
RTC_HISTOGRAM_COMMON_BLOCK_SLOW.

The macro RTC_HISTOGRAM_COMMON_BLOCK uses a static variable for caching,
which causes its usage to behave unlike that of a regular method,
introducing subtble bugs. For example, if this macro is used inside a
member function to log an instance-dependent metric, all instances of
the same class will share the same cached histogram handle and thus
incorrect reports. Before we move away from these macro-based
implementation for metrics, we should avoid using the non-slow macro
unless the caching in logging metrics become performance-critical.

Bug: webrtc:10188, chromium:921023
Change-Id: I8835978498f3e67c5d97580fc916792f38817ff5
Reviewed-on: https://webrtc-review.googlesource.com/c/118022
Commit-Queue: Minyue Li <minyue@webrtc.org>
Reviewed-by: Minyue Li <minyue@webrtc.org>
Reviewed-by: Niels Moller <nisse@webrtc.org>
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26334}

system_wrappers/include/metrics.h

diff --git a/system_wrappers/include/metrics.h b/system_wrappers/include/metrics.h
index 6b29018..bad0f65 100644
--- a/system_wrappers/include/metrics.h
+++ b/system_wrappers/include/metrics.h
@@ -134,7 +134,7 @@
 // TODO(qingsi): Refactor the default implementation given by RtcHistogram,
 // which is already sparse, and remove the boundary argument from the macro.
 #define RTC_HISTOGRAM_ENUMERATION_SPARSE(name, sample, boundary) \
-  RTC_HISTOGRAM_COMMON_BLOCK(                                    \
+  RTC_HISTOGRAM_COMMON_BLOCK_SLOW(                               \
       name, sample,                                              \
       webrtc::metrics::SparseHistogramFactoryGetEnumeration(name, boundary))
 
@@ -149,7 +149,7 @@
 // Histogram for enumerators (evenly spaced buckets).
 // |boundary| should be above the max enumerator sample.
 #define RTC_HISTOGRAM_ENUMERATION(name, sample, boundary) \
-  RTC_HISTOGRAM_COMMON_BLOCK(                             \
+  RTC_HISTOGRAM_COMMON_BLOCK_SLOW(                        \
       name, sample,                                       \
       webrtc::metrics::HistogramFactoryGetEnumeration(name, boundary))
 
@@ -176,7 +176,6 @@
     }                                                                      \
   } while (0)
 
-// Deprecated.
 // The histogram is constructed/found for each call.
 // May be used for histograms with infrequent updates.`
 #define RTC_HISTOGRAM_COMMON_BLOCK_SLOW(name, sample, factory_get_invocation) \