[tracing] Reland of Throttle rate of heavy dumps and support to request light/heavy dumps

base/trace_event/memory_dump_provider.h

Index: base/trace_event/memory_dump_provider.h
diff --git a/base/trace_event/memory_dump_provider.h b/base/trace_event/memory_dump_provider.h
index 02c2c737cc8e6455d9fcb248716f28b1f49d3284..6ab20aa1c543116896450b2bb641fc478c4e8c2a 100644
--- a/base/trace_event/memory_dump_provider.h
+++ b/base/trace_event/memory_dump_provider.h
@@ -17,7 +17,11 @@ class ProcessMemoryDump;
 // should generate on dump request. This is to control the size of dumps
 // generated.
 struct MemoryDumpArgs {
-  enum class LevelOfDetail { LOW, HIGH };
+  enum class LevelOfDetail {
+    LOW,
+    HIGH,
+    LAST = HIGH  // For IPC Macros.
+  };
 
   LevelOfDetail level_of_detail;
 };