Disable DiceBrowserTest.NoDiceFromWebUI.

Multiple recent failures:

Win7 Tests (1)
- https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win7%20Tests%20%281%29/84175
- https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win7%20Tests%20%281%29/84165

See failure log on the bug.

TBR=droger@chromium.org

Bug: 879443
Change-Id: Id3300df55adc2336c338cfeb0a3fd8c8e75d51b9
Reviewed-on: https://chromium-review.googlesource.com/1254562Reviewed-by: François Doray <fdoray@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595463}

chrome/browser/signin/dice_browsertest.cc

@@ -782,7 +782,12 @@ IN_PROC_BROWSER_TEST_F(DiceBrowserTest, SignoutAllAccounts) {
 
 // Checks that Dice request header is not set from request from WebUI.
 // See https://crbug.com/428396
-IN_PROC_BROWSER_TEST_F(DiceBrowserTest, NoDiceFromWebUI) {
+#if defined(OS_WIN)
+#define MAYBE_NoDiceFromWebUI DISABLED_NoDiceFromWebUI
+#else
+#define MAYBE_NoDiceFromWebUI NoDiceFromWebUI
+#endif
+IN_PROC_BROWSER_TEST_F(DiceBrowserTest, MAYBE_NoDiceFromWebUI) {
   // Navigate to Gaia and from the native tab, which uses an extension.
   ui_test_utils::NavigateToURL(browser(), GURL("chrome:chrome-signin"));