[webhid] Avoid DCHECK when revoking device permission

content::HidService incorrectly decrements the active frame
count when revoking a permission for a device with no open
connections. This CL changes the behavior so the active frame
count is only decremented if a connection was closed as a
result of revoking the permission.

BUG=1137031

Change-Id: I686d1e11193991c8e5ddeb7a90d50c77b848fe53
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2463997
Commit-Queue: Matt Reynolds <mattreynolds@chromium.org>
Commit-Queue: Reilly Grant <reillyg@chromium.org>
Reviewed-by: Reilly Grant <reillyg@chromium.org>
Auto-Submit: Matt Reynolds <mattreynolds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#815893}

content/browser/hid/hid_service.cc

@@ -183,22 +183,25 @@ void HidService::OnPermissionRevoked(const url::Origin& requesting_origin,
   WebContents* web_contents =
       WebContents::FromRenderFrameHost(render_frame_host());
 
-  base::EraseIf(watcher_ids_, [&](const auto& watcher_entry) {
-    const auto* device_info =
-        delegate->GetDeviceInfo(web_contents, watcher_entry.first);
-    if (!device_info)
-      return true;
-
-    if (delegate->HasDevicePermission(web_contents, origin(), *device_info)) {
-      return false;
-    }
-
-    watchers_.Remove(watcher_entry.second);
-    return true;
-  });
+  size_t watchers_removed =
+      base::EraseIf(watcher_ids_, [&](const auto& watcher_entry) {
+        const auto* device_info =
+            delegate->GetDeviceInfo(web_contents, watcher_entry.first);
+        if (!device_info)
+          return true;
+
+        if (delegate->HasDevicePermission(web_contents, origin(),
+                                          *device_info)) {
+          return false;
+        }
+
+        watchers_.Remove(watcher_entry.second);
+        return true;
+      });
 
   // If needed decrement the active frame count.
-  OnWatcherRemoved(false /* cleanup_watcher_ids */);
+  if (watchers_removed)
+    OnWatcherRemoved(/*cleanup_watcher_ids=*/false);
 }
 
 void HidService::FinishGetDevices(

content/browser/hid/hid_service_unittest.cc

@@ -388,4 +388,19 @@ TEST_F(HidServiceTest, RevokeDevicePermission) {
   EXPECT_FALSE(connection.is_connected());
 }
 
+TEST_F(HidServiceTest, RevokeDevicePermissionWithoutConnection) {
+  NavigateAndCommit(GURL(kTestUrl));
+
+  mojo::Remote<blink::mojom::HidService> service;
+  contents()->GetMainFrame()->GetHidService(
+      service.BindNewPipeAndPassReceiver());
+
+  // Simulate user revoking permission.
+  url::Origin origin = url::Origin::Create(GURL(kTestUrl));
+  hid_delegate().OnPermissionRevoked(origin, origin);
+
+  base::RunLoop().RunUntilIdle();
+  EXPECT_FALSE(contents()->IsConnectedToHidDevice());
+}
+
 }  // namespace content