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NOTE: This a reland of [1] which got reverted in [2].

This CL introduces the TraceArguments helper class to simplify
the way TRACE_EVENTXXX macro named arguments are passed to the
trace log. By using a small dedicated data structure, it is
possible to generate less code at each trace call site,
compared to the old way that relies on passing 5 specially
crafted arguments to TraceLog methods.

For example, this optimization can save about 12 kiB in
libmonochrome.so for the 32-bit ARM build of Chrome on Android.
For more details, see corresponding bug entry.

This CL does the following:

- Introduce the new class in base/trace_event/trace_arguments.h

- Move the definition of TraceValue to trace_arguments.h and
  augment the union with templated methods to support easy
  initialization from a large set of C++ value types.

- Add new TraceLog methods to add trace events using an
  optional TraceArguments parameter, instead of a bag of
  5 ones (count + names + types + values + convertables).

- Simplify internal templates using C++11 universal references
  and std::forward<> to remove special-casing convertable
  arguments in trace event calls.

- Remove the now obsolete TraceValueUnion type from trace_event.h

- Update base/trace_event/ code to use TraceArguments and the
  new TraceEvent move operations.

- Note that this keeps a few forwarding data types, values and
  methods to avoid other direct callers from the Chromium tree,
  these will be updated in future CLs. One Blink header needs
  to be modified though because it specializes a template
  defined in trace_arguments.h, to support sending WTF::CString
  references as trace arguments.

BUG=898794
R=oysteine@chromium.org,chiniforooshan@chromium.org,alexiln@chromium.org,primiano@chromium.org,torne@chromium.org
TBR=torne@chromium.org,primiano@chromium.org

[1] https://chromium-review.googlesource.com/c/1298997
[2] https://chromium-review.googlesource.com/c/1305250

Change-Id: I67fa434ab1c29b65abd0f327d1c9d27973f54f6a
Reviewed-on: https://chromium-review.googlesource.com/c/1318919
Commit-Queue: David Turner <digit@chromium.org>
Reviewed-by: Alexandr Ilin <alexilin@chromium.org>
Reviewed-by: oysteine <oysteine@chromium.org>
Reviewed-by: David Turner <digit@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615099}