BASELINE: Update Chromium to 78.0.3904.130

Change-Id: If185e0c0061b3437531c97c9c8c78f239352a68b
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>

1 files changed, 14 insertions, 1 deletions

diff --git a/chromium/base/sampling_heap_profiler/poisson_allocation_sampler.h b/chromium/base/sampling_heap_profiler/poisson_allocation_sampler.h
index 3178ef7be83..6006bff19b6 100644
--- a/chromium/base/sampling_heap_profiler/poisson_allocation_sampler.h
+++ b/chromium/base/sampling_heap_profiler/poisson_allocation_sampler.h
@@ -12,6 +12,7 @@
 #include "base/macros.h"
 #include "base/sampling_heap_profiler/lock_free_address_hash_set.h"
 #include "base/synchronization/lock.h"
+#include "base/thread_annotations.h"
 
 namespace base {
 
@@ -77,6 +78,13 @@ class BASE_EXPORT PoissonAllocationSampler {
   static void SetHooksInstallCallback(void (*hooks_install_callback)());
 
   void AddSamplesObserver(SamplesObserver*);
+
+  // Note: After an observer is removed it is still possible to receive
+  // a notification to that observer. This is not a problem currently as
+  // the only client of this interface is the base::SamplingHeapProfiler,
+  // which is a singleton.
+  // If there's a need for this functionality in the future, one might
+  // want to put observers notification loop under a reader-writer lock.
   void RemoveSamplesObserver(SamplesObserver*);
 
   void SetSamplingInterval(size_t sampling_interval);
@@ -109,7 +117,12 @@ class BASE_EXPORT PoissonAllocationSampler {
   void BalanceAddressesHashSet();
 
   Lock mutex_;
-  std::vector<SamplesObserver*> observers_;
+  // The |observers_| list is guarded by |mutex_|, however a copy of it
+  // is made before invoking the observers (to avoid performing expensive
+  // operations under the lock) as such the SamplesObservers themselves need
+  // to be thread-safe and support being invoked racily after
+  // RemoveSamplesObserver().
+  std::vector<SamplesObserver*> observers_ GUARDED_BY(mutex_);
 
   static PoissonAllocationSampler* instance_;