mac: Emit dyld info from the memory dump provider.

components/tracing/common/process_metrics_memory_dump_provider.cc

Index: components/tracing/common/process_metrics_memory_dump_provider.cc
diff --git a/components/tracing/common/process_metrics_memory_dump_provider.cc b/components/tracing/common/process_metrics_memory_dump_provider.cc
index f5a9471be463bd3f8429cc719cd8368f25ad46d5..e573ca1a72bc8c4fd56b9d1471ae5fd4b856ba17 100644
--- a/components/tracing/common/process_metrics_memory_dump_provider.cc
+++ b/components/tracing/common/process_metrics_memory_dump_provider.cc
@@ -28,6 +28,7 @@
 #include <libproc.h>
 #include <mach/mach.h>
 #include <mach/mach_vm.h>
+#include <mach/shared_region.h>
 #include <sys/param.h>
 
 #include "base/numerics/safe_math.h"
@@ -257,6 +258,13 @@ bool ProcessMetricsMemoryDumpProvider::DumpProcessMemoryMaps(
     if (info.share_mode == SM_COW && info.ref_count == 1)
       info.share_mode = SM_PRIVATE;
 
+    // Ignore regions in the dyld shared cache.

[Mark Mentovai, 2017/02/03 23:17:13]

Anyone can come along and map something else in this region to hide from our
statistic gathering, accidentally or on purpose. Are there other characteristics
of the region that we can check to make sure that this is likely to be the dyld
shared cache region? A dedicated user_tag, perhaps? The fact that the top-level
entry is a submap? Anything else?

+    if (address >= SHARED_REGION_BASE_X86_64 &&
+        address < (SHARED_REGION_BASE_X86_64 + SHARED_REGION_SIZE_X86_64) &&
+        info.share_mode != SM_PRIVATE) {
+      continue;
+    }
+
     VMRegion region;
     uint64_t dirty_bytes = info.pages_dirtied * PAGE_SIZE;
     uint64_t clean_bytes =