[Site Muting] Allow user to mute site while in PiP mode

This CL updates the CanToggleAudioMute logic to always return true when
the user is in PiP mode.

Bug: 855686
Change-Id: Iea22547c8c4b50c859f84bf7277d08cdd736309b
Reviewed-on: https://chromium-review.googlesource.com/1112697Reviewed-by: apacible <apacible@chromium.org>
Reviewed-by: Yuri Wiitala <miu@chromium.org>
Commit-Queue: Yuri Wiitala <miu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570232}

chrome/browser/ui/tabs/tab_utils.cc

@@ -376,12 +376,12 @@ bool CanToggleAudioMute(content::WebContents* contents) {
     case TabAlertState::NONE:
     case TabAlertState::AUDIO_PLAYING:
     case TabAlertState::AUDIO_MUTING:
+    case TabAlertState::PIP_PLAYING:
       return true;
     case TabAlertState::MEDIA_RECORDING:
     case TabAlertState::TAB_CAPTURING:
     case TabAlertState::BLUETOOTH_CONNECTED:
     case TabAlertState::USB_CONNECTED:
-    case TabAlertState::PIP_PLAYING:
       // The new Audio Service implements muting separately from the tab audio
       // capture infrastructure; so the mute state can be toggled independently
       // at all times.