Fix comparison of integers of different signs.

This issue can be reproduced with enable_nacl = false on top of linux
chromos build.

Bug: 1126359
Change-Id: I35feda29e79ccb8758e41fe1bb693bfed79c4575
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2577392Reviewed-by: Austin Tankiang <austinct@chromium.org>
Commit-Queue: Leo Lai <cylai@google.com>
Cr-Commit-Position: refs/heads/master@{#834589}

chrome/browser/chromeos/drive/drive_integration_service_browsertest.cc

@@ -142,7 +142,7 @@ IN_PROC_BROWSER_TEST_F(DriveIntegrationServiceBrowserTest,
       drivefs::mojom::QueryParameters::SortDirection::kAscending,
       base::BindLambdaForTesting(
           [=](FileError error, std::vector<base::FilePath> paths) {
-            EXPECT_EQ(2, paths.size());
+            EXPECT_EQ(2u, paths.size());
             EXPECT_EQ("baz", paths[0].BaseName().value());
             EXPECT_EQ("bar", paths[1].BaseName().value());
             quit_closure.Run();