Pass isolate to ScopedPersistent constructor

Pass isolate to ScopedPersistent constructor to avoid implicit call to
v8::Isolate::GetCurrent().

R=haraken
BUG=263412

Review URL: https://chromiumcodereview.appspot.com/23601032

git-svn-id: svn://svn.chromium.org/blink/trunk@157822 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Reland https://codereview.chromium.org/23458023/ which was reverted due to breaking the android_aosp bot. 

What it differs to the original CL is adding #if ENABLE(WEB_AUDIO) around the WebAudio code.

Switch LiveAudio to source provider solution.
This will fix a bunch of LiveAudio issues, and also allow us to feed the remote stream to WebAudio.
From some tests, it seems that we can even get some latency gain on Mac when using the new solution versus the old LiveAudio.

TBR=abarth@chromium.org

BUG=257963
TEST=http://webrtc.googlecode.com/svn/trunk/samples/js/demos/html/webaudio-and-webrtc.html

Review URL: https://chromiumcodereview.appspot.com/24174003

git-svn-id: svn://svn.chromium.org/blink/trunk@157823 bbb929c8-8fbe-4397-9dbb-9b2b20218538