Reland of name kDisableGestureRequirementForMediaPlayback and make it a test-only flag. (patchset #1 id:1 of https://codereview.chromium.org/2851453003/ )

Reason for revert:
Reland the original patch as timvolodine and I believe it's not related to the compile failure early today.

Original issue's description:
> Revert of Rename kDisableGestureRequirementForMediaPlayback and make it a test-only flag. (patchset #2 id:20001 of https://codereview.chromium.org/2843913003/ )
>
> Reason for revert:
> broke clang-clankium-tot-builder crbug.com/716075
>
> (FullscreenWebContentsActivityTest not updated)
>
> Original issue's description:
> > Rename kDisableGestureRequirementForMediaPlayback and make it a test-only flag.
> >
> > The flag should only be set by tests and will allow all autoplay related
> > restrictions such as autoplay policy and background playback to be
> > disabled.
> >
> > BUG=714676
> > CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
> >
> > Review-Url: https://codereview.chromium.org/2843913003
> > Cr-Commit-Position: refs/heads/master@{#467692}
> > Committed: https://chromium.googlesource.com/chromium/src/+/d1f8f6ca6c8b7cdaf02150099ce6db0cfc7223f6
>
> TBR=dalecurtis@chromium.org,jam@chromium.org,mlamouri@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=714676
>
> Review-Url: https://codereview.chromium.org/2851453003
> Cr-Commit-Position: refs/heads/master@{#467715}
> Committed: https://chromium.googlesource.com/chromium/src/+/54e35df000303d1a3b5214db2232aa2fb5c12e3a

TBR=dalecurtis@chromium.org,jam@chromium.org,mlamouri@chromium.org,timvolodine@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=714676

Review-Url: https://codereview.chromium.org/2845973005
Cr-Original-Commit-Position: refs/heads/master@{#467782}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 32d29a10153865441252e100a9781648b8df795b
3 files changed
tree: 3736eb4288aa1fc836c2670fcca9c82591e455f0
  1. accessibility/
  2. android/
  3. auto_bisect/
  4. battor_agent/
  5. binary_size/
  6. bisect_repackage/
  7. blink_rename_merge_helper/
  8. cfi/
  9. check_ecs_deps/
  10. checkbins/
  11. checklicenses/
  12. checkperms/
  13. checkteamtags/
  14. chrome_extensions/
  15. chrome_proxy/
  16. clang/
  17. clang_format_merge_driver/
  18. code_coverage/
  19. codesearch/
  20. compile_test/
  21. copyright_scanner/
  22. coverity/
  23. cr/
  24. cros/
  25. cygprofile/
  26. determinism/
  27. dromaeo_benchmark_runner/
  28. emacs/
  29. find_runtime_symbols/
  30. flakiness/
  31. gdb/
  32. gen_keyboard_overlay_data/
  33. generate_library_loader/
  34. generate_shim_headers/
  35. generate_stubs/
  36. git/
  37. gn/
  38. grit/
  39. gritsettings/
  40. idl_parser/
  41. imagediff/
  42. ipc_fuzzer/
  43. json_comment_eater/
  44. json_schema_compiler/
  45. json_to_struct/
  46. linux/
  47. luci-go/
  48. mac/
  49. mb/
  50. md_browser/
  51. measure_page_load_time/
  52. memory/
  53. memory_inspector/
  54. metrics/
  55. msan/
  56. oopif/
  57. origin_trials/
  58. page_cycler/
  59. perf/
  60. perf_expectations/
  61. polymer/
  62. protoc_wrapper/
  63. python/
  64. real_world_impact/
  65. resource_prefetch_predictor/
  66. resources/
  67. screenshot_testing/
  68. security/
  69. site_compare/
  70. stats_viewer/
  71. strict_enum_value_checker/
  72. sublime/
  73. symsrc/
  74. tcmalloc/
  75. tests/
  76. traceline/
  77. traffic_annotation/
  78. ubsan/
  79. usb_gadget/
  80. valgrind/
  81. variations/
  82. vim/
  83. web_bluetooth/
  84. win/
  85. xdisplaycheck/
  86. bash-completion
  87. bisect-builds.py
  88. bisect-manual-test.py
  89. bisect_test.py
  90. boilerplate.py
  91. check_git_config.py
  92. check_grd_for_unused_strings.py
  93. clang-format-js
  94. DEPS
  95. diagnose-me.py
  96. gypv8sh.py
  97. include_tracer.py
  98. ipc_messages_log.py
  99. licenses.py
  100. multi_process_rss.py
  101. nocompile_driver.py
  102. omahaproxy.py
  103. OWNERS
  104. prepare-bisect-perf-regression.py
  105. remove_duplicate_includes.py
  106. remove_stale_pyc_files.py
  107. roll_angle.py
  108. roll_swiftshader.py
  109. roll_webgl_conformance.py
  110. roll_webrtc.py
  111. run-bisect-manual-test.py
  112. run-bisect-perf-regression.py
  113. run-perf-test.cfg
  114. safely-roll-deps.py
  115. sort-headers.py
  116. sort_sources.py
  117. unused-symbols-report.py
  118. yes_no.py