tp: add experimental flat slice table

This table is useful to do ad-hoc analysis on slices by always giving
the deepest slice on a stack.

Currently still very experimental and is mainly intended for
prototyping. Interface and behaviour is likely to change as we tune the
prototype.

Change-Id: If19f18c1c8bd9c5c09af012cd670e2bc0b1ef74e
diff --git a/BUILD b/BUILD
index 7cdf2d7..3604922 100644
--- a/BUILD
+++ b/BUILD
@@ -1238,6 +1238,8 @@
         "src/trace_processor/dynamic/experimental_counter_dur_generator.h",
         "src/trace_processor/dynamic/experimental_flamegraph_generator.cc",
         "src/trace_processor/dynamic/experimental_flamegraph_generator.h",
+        "src/trace_processor/dynamic/experimental_flat_slice_generator.cc",
+        "src/trace_processor/dynamic/experimental_flat_slice_generator.h",
         "src/trace_processor/dynamic/experimental_sched_upid_generator.cc",
         "src/trace_processor/dynamic/experimental_sched_upid_generator.h",
         "src/trace_processor/dynamic/experimental_slice_layout_generator.cc",