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

base/trace_event/trace_config_unittest.cc

 // Copyright 2015 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 <stddef.h>
 
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
 #include "base/macros.h"
 #include "base/trace_event/memory_dump_manager.h"
@@ skipping 679 matching lines @@
   EXPECT_EQ(
       TraceConfig::MemoryDumpConfig::HeapProfiler ::
           kDefaultBreakdownThresholdBytes,
       tc.memory_dump_config().heap_profiler_options.breakdown_threshold_bytes);
 }
 
 TEST(TraceConfigTest, LegacyStringToMemoryDumpConfig) {
   TraceConfig tc(MemoryDumpManager::kTraceCategory, "");
   EXPECT_TRUE(tc.IsCategoryGroupEnabled(MemoryDumpManager::kTraceCategory));
   EXPECT_NE(std::string::npos, tc.ToString().find("memory_dump_config"));
-  EXPECT_EQ(0u, tc.memory_dump_config().triggers.size());
+  EXPECT_EQ(1u, tc.memory_dump_config().triggers.size());
   EXPECT_EQ(
       TraceConfig::MemoryDumpConfig::HeapProfiler ::
           kDefaultBreakdownThresholdBytes,
       tc.memory_dump_config().heap_profiler_options.breakdown_threshold_bytes);
 }
 
 }  // namespace trace_event
 }  // namespace base