Disable flaky SessionStorageContextMojoTest.ClearDiskState test.

TBR=rockot, pwnall

Bug: 1008697
Change-Id: Id446de794341306a4c65555324e988abcb420383
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1830055Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Auto-Submit: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700984}

content/browser/dom_storage/session_storage_context_mojo_unittest.cc

@@ -1125,7 +1125,8 @@ TEST_F(SessionStorageContextMojoTest, PurgeInactiveWrappers) {
   EXPECT_EQ(0ul, data.size());
 }
 
-TEST_F(SessionStorageContextMojoTest, ClearDiskState) {
+// TODO(https://crbug.com/1008697): Flakes when verifying no data found.
+TEST_F(SessionStorageContextMojoTest, DISABLED_ClearDiskState) {
   SetBackingMode(SessionStorageContextMojo::BackingMode::kClearDiskStateOnOpen);
   std::string namespace_id1 = base::GenerateGUID();
   url::Origin origin1 = url::Origin::Create(GURL("http://foobar.com"));