Disable TabCaptureApiTest.ApiTests flakes on Mac.

Bug: 764464
Tbr: miu@chromium.org
Change-Id: Ibe3cc60266d1c20c79fe6f4b742f882426796ced
Reviewed-on: https://chromium-review.googlesource.com/664065Reviewed-by: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Commit-Queue: Sebastien Seguin-Gagnon <sebsg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501377}

chrome/browser/extensions/api/tab_capture/tab_capture_apitest.cc

@@ -145,8 +145,14 @@ TEST(TabCaptureCaptureOffscreenTabTest, DetermineInitialSize) {
                 options));
 }
 
+// Flaky on Mac. See https://crbug.com/764464.
+#if defined(OS_MACOSX)
+#define MAYBE_ApiTests DISABLED_ApiTests
+#else
+#define MAYBE_ApiTests ApiTests
+#endif
 // Tests API behaviors, including info queries, and constraints violations.
-IN_PROC_BROWSER_TEST_F(TabCaptureApiTest, ApiTests) {
+IN_PROC_BROWSER_TEST_F(TabCaptureApiTest, MAYBE_ApiTests) {
   AddExtensionToCommandLineWhitelist();
   ASSERT_TRUE(RunExtensionSubtest("tab_capture", "api_tests.html")) << message_;
 }