wake lock: Account for lost Mojo connection in MockWakeLock::WaitForCancelation()

WakeLockTest.LossOfDocumentActivity has been flaky since
r803272 ("[HeapMojo] Make HeapMojoWrapperMode::kWithContextObserver
default"), but that CL simply uncovered a bug in MockWakeLock: when the
ExecutionContext is destroyed, MockWakeLock::OnConnectionError() may be
called before we call MockWakeLock::WaitForCancelation(), in which case the
latter will loop forever.

Bail out early if |receiver_| is not bound, which indicates that there has
been a Mojo connection error and MockWakeLock::CancelWakeLock() has already
been called.

Bug: 1123879
Change-Id: Ia2f29fe560a3d7ca49b083dfec01fdcd6c48a504
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2390065
Commit-Queue: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Commit-Queue: Kouhei Ueno <kouhei@chromium.org>
Auto-Submit: Raphael Kubo da Costa <raphael.kubo.da.costa@intel.com>
Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Minoru Chikamune <chikamune@chromium.org>
Cr-Commit-Position: refs/heads/master@{#803852}

third_party/blink/renderer/modules/wake_lock/wake_lock_manager.h

@@ -43,10 +43,8 @@ class MODULES_EXPORT WakeLockManager final
 
   // An actual platform WakeLock. If bound, it means there is an active wake
   // lock for a given type.
-  // TODO(crbug.com/1123879): Resolve the flaky test and make this
-  // kWithoutContextObserver.
   HeapMojoRemote<device::mojom::blink::WakeLock,
-                 HeapMojoWrapperMode::kForceWithoutContextObserver>
+                 HeapMojoWrapperMode::kWithoutContextObserver>
       wake_lock_;
   WakeLockType wake_lock_type_;
 

third_party/blink/renderer/modules/wake_lock/wake_lock_test.cc

@@ -77,7 +77,6 @@ TEST(WakeLockTest, RequestWakeLockDenied) {
   EXPECT_EQ("NotAllowedError", dom_exception->name());
 }
 
-// Test is flaky : http://crbug.com/1123879
 // https://w3c.github.io/wake-lock/#handling-document-loss-of-full-activity
 TEST(WakeLockTest, LossOfDocumentActivity) {
   MockWakeLockService wake_lock_service;

third_party/blink/renderer/modules/wake_lock/wake_lock_test_utils.cc

@@ -100,6 +100,12 @@ void MockWakeLock::WaitForRequest() {
 
 void MockWakeLock::WaitForCancelation() {
   DCHECK(!cancel_wake_lock_callback_);
+  if (!receiver_.is_bound()) {
+    // If OnConnectionError() has been called, bail out early to avoid waiting
+    // forever.
+    DCHECK(!is_acquired_);
+    return;
+  }
   base::RunLoop run_loop;
   cancel_wake_lock_callback_ = run_loop.QuitClosure();
   RunWithStack(&run_loop);