Remove obsolete v8_benchmark. It was replaced with Octane on the perf bots.

chrome/test/data/v8_benchmark/README.txt

-V8 Benchmark Suite
-==================
-
-This is the V8 benchmark suite: A collection of pure JavaScript
-benchmarks that we have used to tune V8. The licenses for the
-individual benchmarks are included in the JavaScript files.
-
-In addition to the benchmarks, the suite consists of the benchmark
-framework (base.js), which must be loaded before any of the individual
-benchmark files, and two benchmark runners: An HTML version (run.html)
-and a standalone JavaScript version (run.js).
-
-
-Changes From Version 1 To Version 2
-===================================
-
-For version 2 the crypto benchmark was fixed.  Previously, the
-decryption stage was given plaintext as input, which resulted in an
-error.  Now, the decryption stage is given the output of the
-encryption stage as input.  The result is checked against the original
-plaintext.  For this to give the correct results the crypto objects
-are reset for each iteration of the benchmark.  In addition, the size
-of the plain text has been increased a little and the use of
-Math.random() and new Date() to build an RNG pool has been removed.
-
-Other benchmarks were fixed to do elementary verification of the
-results of their calculations.  This is to avoid accidentally
-obtaining scores that are the result of an incorrect JavaScript engine
-optimization.
-
-
-Changes From Version 2 To Version 3
-===================================
-
-Version 3 adds a new benchmark, RegExp.  The RegExp benchmark is
-generated by loading 50 of the most popular pages on the web and
-logging all regexp operations performed.  Each operation is given a
-weight that is calculated from an estimate of the popularity of the
-pages where it occurs and the number of times it is executed while
-loading each page.  Finally the literal letters in the data are
-encoded using ROT13 in a way that does not affect how the regexps
-match their input.
-
-
-Changes from Version 3 to Version 4
-===================================
-
-The Splay benchmark is a newcomer in version 4.  It manipulates a
-splay tree by adding and removing data nodes, thus exercising the
-memory management subsystem of the JavaScript engine.
-
-Furthermore, all the unused parts of the Prototype library were
-removed from the RayTrace benchmark. This does not affect the running
-of the benchmark.
-
-
-Changes from Version 4 to Version 5
-===================================
-
-Removed duplicate line in random seed code, and changed the name of
-the Object.prototype.inherits function in the DeltaBlue benchmark to
-inheritsFrom to avoid name clashes when running in Chromium with
-extensions enabled.
-
-
-Changes from Version 5 to Version 6
-===================================
-
-Removed dead code from the RayTrace benchmark and fixed a couple of
-typos in the DeltaBlue implementation. Changed the Splay benchmark to
-avoid converting the same numeric key to a string over and over again
-and to avoid inserting and removing the same element repeatedly thus
-increasing pressure on the memory subsystem. Changed the RegExp
-benchmark to exercise the regular expression engine on different
-input strings.
-
-Furthermore, the benchmark runner was changed to run the benchmarks
-for at least a few times to stabilize the reported numbers on slower
-machines.