[Memory-UMA] Implement basic working prototype.

base/trace_event/memory_allocator_dump.cc

Index: base/trace_event/memory_allocator_dump.cc
diff --git a/base/trace_event/memory_allocator_dump.cc b/base/trace_event/memory_allocator_dump.cc
index 2692521c096ab6213cfe1dd20d2a98e8a91ff6ce..e099f1a53e8e729e852e2cc79fbb3cfceb40daa3 100644
--- a/base/trace_event/memory_allocator_dump.cc
+++ b/base/trace_event/memory_allocator_dump.cc
@@ -86,7 +86,6 @@ void MemoryAllocatorDump::AddString(const char* name,
   // String attributes are disabled in background mode.
   if (process_memory_dump_->dump_args().level_of_detail ==
       MemoryDumpLevelOfDetail::BACKGROUND) {
-    NOTREACHED();

[Primiano Tucci (use gerrit), 2017/05/15 03:48:09]

Hmm why? This shouldn't really happen. If it happens some MDP is broken.
if they are doing an AddString into BACKGROUND mode they will be likely doing
some non-cheap traversal of their structs

[erikchen, 2017/05/15 17:29:15]

Done.

     return;
   }