Bug 1775285 - Counters should output a 0 sample at the beginning of a time without change, r=gerald.

Differential Revision: https://phabricator.services.mozilla.com/D149890

tools/profiler/core/ProfileBufferEntry.cpp

@@ -1812,7 +1812,10 @@ void ProfileBuffer::StreamCountersToJSON(
             // or next sample; Always write the first and last samples.
             if (i == 0 || i == size - 1 ||
                 samples[i].mNumber != previousNumber ||
-                samples[i].mCount != previousCount) {
+                samples[i].mCount != previousCount ||
+                // Ensure we ouput the first 0 before skipping samples.
+                (i >= 2 && (samples[i - 2].mNumber != previousNumber ||
+                            samples[i - 2].mCount != previousCount))) {
               if (i != 0 && samples[i].mTime >= samples[i - 1].mTime) {
                 MOZ_LOG(sFuzzyfoxLog, mozilla::LogLevel::Error,
                         ("Fuzzyfox Profiler Assertion: %f >= %f",

tools/profiler/tests/gtest/GeckoProfiler.cpp

@@ -3493,8 +3493,9 @@ TEST(GeckoProfiler, Counters)
   };
 
   int64_t testCounters[] = {10, 7, -17};
-  NumberAndCount expectedTestCounters[] = {{1u, 10}, {0u, 0},   {1u, 7},
-                                           {0u, 0},  {1u, -17}, {0u, 0}};
+  NumberAndCount expectedTestCounters[] = {{1u, 10}, {0u, 0}, {1u, 7},
+                                           {0u, 0},  {0u, 0}, {1u, -17},
+                                           {0u, 0},  {0u, 0}};
   constexpr size_t expectedTestCountersCount =
       MOZ_ARRAY_LENGTH(expectedTestCounters);