memory-infra: Remove is_enabled_ from MDM

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 2e3f36d225b1a5e3ed402b50dac35b8caa67d9ef..822be9281f4251d6534e35feabca143cf72b894f 100644
--- a/base/trace_event/memory_dump_manager.cc
+++ b/base/trace_event/memory_dump_manager.cc
@@ -157,7 +157,6 @@ void MemoryDumpManager::SetInstanceForTesting(MemoryDumpManager* instance) {
 
 MemoryDumpManager::MemoryDumpManager()
     : is_coordinator_(false),
-      is_enabled_(0),
       tracing_process_id_(kInvalidTracingProcessId),
       dumper_registrations_ignored_for_testing_(false),
       heap_profiling_enabled_(false) {
@@ -404,15 +403,12 @@ void MemoryDumpManager::RequestGlobalDump(
     MemoryDumpType dump_type,
     MemoryDumpLevelOfDetail level_of_detail,
     const GlobalMemoryDumpCallback& callback) {
-  // Bail out immediately if tracing is not enabled at all or if the dump mode
-  // is not allowed.
-  if (!UNLIKELY(subtle::NoBarrier_Load(&is_enabled_)) ||
-      !IsDumpModeAllowed(level_of_detail)) {
-    VLOG(1) << kLogPrefix << " failed because " << kTraceCategory
-            << " tracing category is not enabled or the requested dump mode is "
+  if (!IsDumpModeAllowed(level_of_detail) &&
+      dump_type != MemoryDumpType::SUMMARY_ONLY) {
+    VLOG(1) << kLogPrefix
+            << " failed because the requested dump mode is "
                "not allowed by trace config.";
-    if (!callback.is_null())
-      callback.Run(0u /* guid */, false /* success */);
+    callback.Run(0u /* guid */, false /* success */);
     return;
   }
 

[ssid, 2017/05/04 22:00:22]

DCHECK(dump_type != SUMMARY_ONLY || level_of_detail == BACKGROUND);

[hjd, 2017/05/05 14:54:52]

Done.

@@ -498,6 +494,12 @@ void MemoryDumpManager::CreateProcessDump(
   {
     AutoLock lock(lock_);
 
+    if (args.level_of_detail == MemoryDumpLevelOfDetail::DETAILED &&

[ssid, 2017/05/04 22:00:22]

Comment here saying:
MDM could have been disabled before reaching to this point. Since PMD will
expect session state if heap profiling is enabled, return without creating the
dump.

Thinking more on this I realized in future we could have heap profiling with
background mode for slow reports. So, a better condition would be args.dump_type
!= SUMMARY_ONLY. Sorry for the back and forth.

[hjd, 2017/05/05 14:54:52]

Done.

+        heap_profiling_enabled_ && !session_state_) {
+      callback.Run(args.dump_guid, false /* success */, base::nullopt);
+      return;
+    }
+
     pmd_async_state.reset(new ProcessMemoryDumpAsyncState(
         args, dump_providers_, session_state_, callback,
         GetOrCreateBgTaskRunnerLocked()));
@@ -534,22 +536,6 @@ void MemoryDumpManager::SetupNextMemoryDump(
   // (for discounting trace memory overhead) while holding the |lock_|.
   TraceLog::GetInstance()->InitializeThreadLocalEventBufferIfSupported();
 
-  // MDM might have been disabled before getting to this point.
-  // Anyway either MDM is disabled or this was the last hop, create a trace
-  // event, add it to the trace and finalize process dump invoking the callback.
-  if (!subtle::NoBarrier_Load(&is_enabled_)) {
-    if (pmd_async_state->pending_dump_providers.empty()) {
-      VLOG(1) << kLogPrefix << " failed because MemoryDumpManager was disabled"
-              << " before finalizing the dump";
-    } else {
-      VLOG(1) << kLogPrefix << " failed because MemoryDumpManager was disabled"
-              << " before dumping "
-              << pmd_async_state->pending_dump_providers.back().get()->name;
-    }
-    pmd_async_state->dump_successful = false;
-    pmd_async_state->pending_dump_providers.clear();
-  }
-
   if (pmd_async_state->pending_dump_providers.empty())
     return FinalizeDumpAndAddToTrace(std::move(pmd_async_state));
 
@@ -809,8 +795,6 @@ void MemoryDumpManager::Enable(
   DCHECK(!request_dump_function_.is_null());
   session_state_ = session_state;
 
-  subtle::NoBarrier_Store(&is_enabled_, 1);
-
   MemoryDumpScheduler::Config periodic_config;
   bool peak_detector_configured = false;
   for (const auto& trigger : memory_dump_config.triggers) {
@@ -861,15 +845,11 @@ void MemoryDumpManager::Disable() {
   // There might be a memory dump in progress while this happens. Therefore,
   // ensure that the MDM state which depends on the tracing enabled / disabled
   // state is always accessed by the dumping methods holding the |lock_|.
-  if (!subtle::NoBarrier_Load(&is_enabled_))
-    return;
-  subtle::NoBarrier_Store(&is_enabled_, 0);
-  {
-    AutoLock lock(lock_);
-    MemoryDumpScheduler::GetInstance()->Stop();
-    MemoryPeakDetector::GetInstance()->TearDown();
-    session_state_ = nullptr;
-  }
+  AutoLock lock(lock_);
+
+  MemoryDumpScheduler::GetInstance()->Stop();
+  MemoryPeakDetector::GetInstance()->TearDown();
+  session_state_ = nullptr;
 }
 
 bool MemoryDumpManager::IsDumpModeAllowed(MemoryDumpLevelOfDetail dump_mode) {