Revert of Change memory dumps to not use periodic dumps by default.

base/trace_event/memory_dump_manager_unittest.cc

Index: base/trace_event/memory_dump_manager_unittest.cc
diff --git a/base/trace_event/memory_dump_manager_unittest.cc b/base/trace_event/memory_dump_manager_unittest.cc
index fe1b2fe5ac8a1e9fd3102af8b4488a6cdce4d859..9806c5008ec4bd563b33b6e9278f90c5e5729872 100644
--- a/base/trace_event/memory_dump_manager_unittest.cc
+++ b/base/trace_event/memory_dump_manager_unittest.cc
@@ -980,17 +980,17 @@
       .WillByDefault(Return());
 
   // Enabling memory-infra with the legacy TraceConfig (category filter) in
-  // a coordinator process should not enable periodic dumps.
-  EnableTracingWithLegacyCategories(MemoryDumpManager::kTraceCategory);
-  EXPECT_FALSE(IsPeriodicDumpingEnabled());
+  // a coordinator process should enable periodic dumps.
+  EnableTracingWithLegacyCategories(MemoryDumpManager::kTraceCategory);
+  EXPECT_TRUE(IsPeriodicDumpingEnabled());
   DisableTracing();
 
   // Enabling memory-infra with the new (JSON) TraceConfig in a coordinator
-  // process while specifying a "memory_dump_config" section should enable
+  // process without specifying any "memory_dump_config" section should enable
   // periodic dumps. This is to preserve the behavior chrome://tracing UI, that
-  // is: ticking memory-infra should dump periodically with an explicit config.
+  // is: ticking memory-infra should dump periodically with the default config.
   EnableTracingWithTraceConfig(
-      TraceConfigMemoryTestUtil::GetTraceConfig_PeriodicTriggers(100, 5));
+      TraceConfigMemoryTestUtil::GetTraceConfig_NoTriggers());
   EXPECT_TRUE(IsPeriodicDumpingEnabled());
   DisableTracing();