[Build] Fix chromeos-kevin-builder-perf-fyi compile failure.

Compile failure in AppServiceAppWindowArcAppBrowserTest.LogicalWindowId
arises from signed / unsigned comparison: std::count_if() returns a
signed type, but the EXPECT_EQ used an unsigned value.

This issue has been causing Builder chromeos-kevin-builder-perf-fyi to
fail since start of 2020-06.

Bug: 1106626
Change-Id: I4278161ad2533ac566bf78851ceedbada841fa6d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2302834Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Reviewed-by: Philipp Weiß <phweiss@chromium.org>
Commit-Queue: Samuel Huang <huangs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789991}

chrome/browser/ui/ash/launcher/app_service/app_service_app_window_browsertest.cc

@@ -640,7 +640,7 @@ IN_PROC_BROWSER_TEST_F(AppServiceAppWindowArcAppBrowserTest, LogicalWindowId) {
   auto is_hidden = [](aura::Window* w) {
     return w->GetProperty(ash::kHideInShelfKey);
   };
-  EXPECT_EQ(1u, std::count_if(windows.begin(), windows.end(), is_hidden));
+  EXPECT_EQ(1, std::count_if(windows.begin(), windows.end(), is_hidden));
 
   // The hidden window should be task_id 2.
   aura::Window* window1 =
@@ -670,7 +670,7 @@ IN_PROC_BROWSER_TEST_F(AppServiceAppWindowArcAppBrowserTest, LogicalWindowId) {
   app_host()->OnTaskDestroyed(1);
   windows = app_service_proxy_->InstanceRegistry().GetWindows(app_id);
   EXPECT_EQ(1u, windows.size());
-  EXPECT_EQ(0u, std::count_if(windows.begin(), windows.end(), is_hidden));
+  EXPECT_EQ(0, std::count_if(windows.begin(), windows.end(), is_hidden));
 
   // Close second window.
   app_host()->OnTaskDestroyed(2);