[tracing] Switch to new heap dump format.

This CL switches tracing to a new heap dump format, that offers the
following advantages:

1. Dumps include all the information collected by Chrome's heap profiler.

2. The format is simpler and more compact.

3. The format can easily be extended to include additional per-entry data.

4. The format allows for post-processing (see recategorization from
   crrev.com/2906413002 as an example).

BUG=708930

Review-Url: https://codereview.chromium.org/2650863003
Cr-Original-Commit-Position: refs/heads/master@{#480580}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: d4a5e98235da0cc8c4fb1ae2f67826b0b480ce4c

tools/gn/bootstrap/bootstrap.py

diff --git a/tools/gn/bootstrap/bootstrap.py b/tools/gn/bootstrap/bootstrap.py
index dd564ac..730d5a6 100755
--- a/tools/gn/bootstrap/bootstrap.py
+++ b/tools/gn/bootstrap/bootstrap.py
@@ -536,6 +536,7 @@
       'base/trace_event/heap_profiler_heap_dump_writer.cc',
       'base/trace_event/heap_profiler_serialization_state.cc',
       'base/trace_event/heap_profiler_stack_frame_deduplicator.cc',
+      'base/trace_event/heap_profiler_string_deduplicator.cc',
       'base/trace_event/heap_profiler_type_name_deduplicator.cc',
       'base/trace_event/malloc_dump_provider.cc',
       'base/trace_event/memory_allocator_dump.cc',