Enable PFFFT for Chrome OS and Fuchsia

Benchmarking on both amd64 and arm Chromebooks shows that PFFFT gives a
performance improvement on Web Audio tests requiring FFTs.

Using the Web Audio Bench at https://spotify.github.io/web-audio-bench/

Dell Chromebook 11 3189 (amd64):

TEST                    Base    PFFFT   Change
Convolver-128f-3ms      3866    3555    -8.04%
Convolver-1024f-23ms    10064   8222    -18.30%
Convolver-2048f-46ms    12236   9671    -20.96%
Convolver-32768f-743ms  26130   19417   -25.69%

Lenovo Yoga N23 (arm):

TEST                    Base    PFFFT   Change
Convolver-128f-3ms      5372    5382    +0.19%
Convolver-1024f-23ms    10489   9234    -11.96%
Convolver-2048f-46ms    12336   10554   -14.45%
Convolver-32768f-743ms  25722   20272   -21.19%

Bug: 1021027
Change-Id: Ieb5cd7af32d632bf252fcbad2101c1a5d2b91970
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1893203Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Raymond Toy <rtoy@chromium.org>
Commit-Queue: Andrew MacPherson <andrew.macpherson@soundtrap.com>
Cr-Commit-Position: refs/heads/master@{#712955}

third_party/blink/renderer/config.gni

@@ -14,10 +14,9 @@ if (current_cpu == "arm") {
 }
 
 declare_args() {
-  # If true, use PFFFT for WebAudio FFT support.  This can be used for
-  # any Android architecture and also Linux and Windows.  Do not use for Mac
-  # because the FFT library there is much faster.
-  use_webaudio_pffft = is_android || target_os == "linux" || target_os == "win"
+  # If true, use PFFFT for WebAudio FFT support. Do not use for Mac because the
+  # FFT library there is much faster.
+  use_webaudio_pffft = target_os != "mac"
 }
 
 declare_args() {