Reland of "[tracing] Add browser-side tests for memory dumps."

base/trace_event/memory_dump_manager.cc

Index: base/trace_event/memory_dump_manager.cc
diff --git a/base/trace_event/memory_dump_manager.cc b/base/trace_event/memory_dump_manager.cc
index f6e0239a215393866b2537800aab4931cfa77153..1c3c581d8ebece634081ce613e1057a0d0d70111 100644
--- a/base/trace_event/memory_dump_manager.cc
+++ b/base/trace_event/memory_dump_manager.cc
@@ -97,7 +97,8 @@ MemoryDumpManager::MemoryDumpManager()
       memory_tracing_enabled_(0),
       tracing_process_id_(kInvalidTracingProcessId),
       system_allocator_pool_name_(nullptr),
-      skip_core_dumpers_auto_registration_for_testing_(false) {
+      skip_core_dumpers_auto_registration_for_testing_(false),
+      disable_periodic_dumps_for_testing_(false) {
   g_next_guid.GetNext();  // Make sure that first guid is not zero.
 }
 
@@ -423,9 +424,11 @@ void MemoryDumpManager::OnTraceLogEnabled() {
   // TODO(primiano): This is a temporary hack to disable periodic memory dumps
   // when running memory benchmarks until they can be enabled/disabled in
   // base::trace_event::TraceConfig. See https://goo.gl/5Hj3o0.
+  // The same mechanism should be used to disable periodic dumps in tests.
   if (delegate_->IsCoordinatorProcess() &&
       !CommandLine::ForCurrentProcess()->HasSwitch(
-          "enable-memory-benchmarking")) {
+          "enable-memory-benchmarking") &&
+      !disable_periodic_dumps_for_testing_) {
     g_periodic_dumps_count = 0;
     periodic_dump_timer_.Start(FROM_HERE,
                                TimeDelta::FromMilliseconds(kDumpIntervalMs),