[memory-infra] Log reasons for memory dump failure

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 4e2cc606e9b8e04396ea06f6da46a75595fb76ae..50171e5715f8399cb9b31b86230d39e8b273a345 100644
--- a/base/trace_event/memory_dump_manager.cc
+++ b/base/trace_event/memory_dump_manager.cc
@@ -337,6 +337,8 @@ void MemoryDumpManager::RequestGlobalDump(
     const MemoryDumpCallback& callback) {
   // Bail out immediately if tracing is not enabled at all.
   if (!UNLIKELY(subtle::NoBarrier_Load(&memory_tracing_enabled_))) {
+    VLOG(1) << "Global memory dump failed because " << kTraceCategory

[Primiano Tucci (use gerrit), 2016/06/08 18:00:45]

I'd say s/Global memory dump/memory-infra dump/.
Imagine this shows in the log, more people know what memory-infra is. "GLobal
memory dump" is more obscure, can sound like a crash reporting thing.

[petrcermak, 2016/06/09 09:46:09]

Done.

+            << " tracing category is not enabled";
     if (!callback.is_null())
       callback.Run(0u /* guid */, false /* success */);
     return;
@@ -422,6 +424,11 @@ void MemoryDumpManager::SetupNextMemoryDump(
   // Anyway either tracing is stopped or this was the last hop, create a trace
   // event, add it to the trace and finalize process dump invoking the callback.
   if (!pmd_async_state->dump_thread_task_runner.get()) {
+    VLOG(1)
+        << "Global memory dump failed because dump thread was destroyed before "

[Primiano Tucci (use gerrit), 2016/06/08 18:00:45]

you probably want to make "Global Memory Dump" (or the new suggestion) a
kConstant, so you are guaranteed that you can grep for that constatn in the logs
and they will all start with the same prefix.

[petrcermak, 2016/06/09 09:46:09]

Done.

+        << (pmd_async_state->pending_dump_providers.empty()
+                ? "finalizing memory dump"
+                : pmd_async_state->pending_dump_providers.back().get()->name);
     pmd_async_state->dump_successful = false;
     pmd_async_state->pending_dump_providers.clear();
   }
@@ -596,8 +603,10 @@ void MemoryDumpManager::FinalizeDumpAndAddToTrace(
 
   bool tracing_still_enabled;
   TRACE_EVENT_CATEGORY_GROUP_ENABLED(kTraceCategory, &tracing_still_enabled);
-  if (!tracing_still_enabled)
+  if (!tracing_still_enabled) {
     pmd_async_state->dump_successful = false;
+    VLOG(1) << "Memory dump failed: Tracing is not enabled any more";

[Primiano Tucci (use gerrit), 2016/06/08 18:00:45]

I'd say here: tracing disabled before the memory dump was completed.

[petrcermak, 2016/06/09 09:46:09]

Done.

+  }
 
   if (!pmd_async_state->callback.is_null()) {
     pmd_async_state->callback.Run(dump_guid, pmd_async_state->dump_successful);