Track thread activities in order to diagnose hangs.

base/BUILD.gn

Index: base/BUILD.gn
diff --git a/base/BUILD.gn b/base/BUILD.gn
index 6ac9562e43817be975e671694b03d2218650b180..25f588d9e9ee85c2d9b030be912139f730473bcd 100644
--- a/base/BUILD.gn
+++ b/base/BUILD.gn
@@ -279,6 +279,10 @@ component("base") {
     # This file depends on files from the "debug/allocator" target,
     # but this target does not depend on "debug/allocator" (see
     # allocator.gyp for details).
+    "debug/activity_analyzer.cc",
+    "debug/activity_analyzer.h",
+    "debug/activity_tracker.cc",
+    "debug/activity_tracker.h",
     "debug/leak_annotations.h",
     "debug/leak_tracker.h",
     "debug/proc_maps_linux.cc",
@@ -1745,6 +1749,8 @@ test("base_unittests") {
     "containers/small_map_unittest.cc",
     "containers/stack_container_unittest.cc",
     "cpu_unittest.cc",
+    "debug/activity_analyzer_unittest.cc",
+    "debug/activity_tracker_unittest.cc",
     "debug/crash_logging_unittest.cc",
     "debug/debugger_unittest.cc",
     "debug/leak_tracker_unittest.cc",