autotest_private: support PIP window state for ARC windows

This CL adds support for PIP (Picture in Picture) window state when
querying ARC window state via autotest_private_api.

This is needed because we are replacing "dumpsys" with "dumpsys --proto"
and "dumpsys --proto" does include the PIP state.
And besides that, it is better to query Ash, than Android, for ARC
states.

TEST=Calling "ash.GetARCAppWindowState" from Tast returns PIP on PIP ARC
     windows.
BUG=chromium:1000774

Change-Id: I4096ab205836f3f3f8b1d4eb964321dd62df77dc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1785058Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Ricardo Quesada <ricardoq@chromium.org>
Auto-Submit: Ricardo Quesada <ricardoq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693345}

chrome/browser/chromeos/extensions/autotest_private/autotest_private_api.cc

@@ -391,6 +391,8 @@ api::autotest_private::WindowStateType ToWindowStateType(
     case ash::WindowStateType::kRightSnapped:
       return api::autotest_private::WindowStateType::
           WINDOW_STATE_TYPE_RIGHTSNAPPED;
+    case ash::WindowStateType::kPip:
+      return api::autotest_private::WindowStateType::WINDOW_STATE_TYPE_PIP;
     default:
       NOTREACHED();
       return api::autotest_private::WindowStateType::WINDOW_STATE_TYPE_NONE;

chrome/common/extensions/api/autotest_private.idl

@@ -55,7 +55,8 @@ namespace autotestPrivate {
     Maximized,
     Fullscreen,
     LeftSnapped,
-    RightSnapped
+    RightSnapped,
+    PIP
   };
 
   // A subset of WM event types in ash::WMEventType. We may add more in the