memory-infra: Add peak-detector skeleton.

base/trace_event/memory_dump_provider_info.h

Index: base/trace_event/memory_dump_provider_info.h
diff --git a/base/trace_event/memory_dump_provider_info.h b/base/trace_event/memory_dump_provider_info.h
index 0f7ca7cc96f96bf5ceda43bf22bd9ea48116e0bb..ca63a987b2c4398a3c734001b19c7de1c886f8b0 100644
--- a/base/trace_event/memory_dump_provider_info.h
+++ b/base/trace_event/memory_dump_provider_info.h
@@ -8,6 +8,7 @@
 #include <memory>
 #include <set>
 
+#include "base/base_export.h"
 #include "base/memory/ref_counted.h"
 #include "base/trace_event/memory_dump_provider.h"
 
@@ -41,7 +42,7 @@ namespace trace_event {
 //   MDM::SetupNextMemoryDump() or MDM::InvokeOnMemoryDump(), when the copy
 //   inside ProcessMemoryDumpAsyncState is erase()-d.
 // - The PeakDetector can keep extra refptrs when enabled.
-struct MemoryDumpProviderInfo
+struct BASE_EXPORT MemoryDumpProviderInfo
     : public RefCountedThreadSafe<MemoryDumpProviderInfo> {
  public:
   // Define a total order based on the |task_runner| affinity, so that MDPs