Disable DownloadDangerPromptTest.TestAll on Windows for flaky timeouts.

BUG=446696
TBR=asanka@chromium.org

Review URL: https://codereview.chromium.org/838673003

Cr-Commit-Position: refs/heads/master@{#310199}

chrome/browser/download/download_danger_prompt_browsertest.cc

@@ -101,7 +101,13 @@ class DownloadDangerPromptTest : public InProcessBrowserTest {
   DISALLOW_COPY_AND_ASSIGN(DownloadDangerPromptTest);
 };
 
-IN_PROC_BROWSER_TEST_F(DownloadDangerPromptTest, TestAll) {
+// Disabled for flaky timeouts on Windows. crbug.com/446696
+#if defined(OS_WIN)
+#define MAYBE_TestAll DISABLED_TestAll
+#else
+#define MAYBE_TestAll TestAll
+#endif
+IN_PROC_BROWSER_TEST_F(DownloadDangerPromptTest, MAYBE_TestAll) {
   // ExperienceSampling: Set default actions for DownloadItem methods we need.
   ON_CALL(download(), GetURL()).WillByDefault(ReturnRef(GURL::EmptyGURL()));
   ON_CALL(download(), GetReferrerUrl())