Disabled PrerenderTest tests on Android.

The following tests are flaky on Android Marshmallow 64 bit tester:
LinkManagerAddTwiceCancelTwice
LinkManagerAddTwiceAbandonTwiceUseTwice

TBR=tbansal@chromium.org,pasko@chromium.org

Bug: 1087876
Change-Id: Ib6e55c4820f1d79723303182e9b2b220d4d2e26c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2225476Reviewed-by: Salvador Guerrero <salg@google.com>
Commit-Queue: Salvador Guerrero <salg@google.com>
Cr-Commit-Position: refs/heads/master@{#773816}

chrome/browser/prerender/prerender_unittest.cc

@@ -1536,7 +1536,14 @@ TEST_F(PrerenderTest, LinkManagerAbandonThenCancel) {
   ASSERT_FALSE(prerender_manager()->FindEntry(url));
 }
 
-TEST_F(PrerenderTest, LinkManagerAddTwiceCancelTwice) {
+// Flaky on Android, crbug.com/1087876.
+#if defined(OS_ANDROID)
+#define MAYBE_LinkManagerAddTwiceCancelTwice \
+  DISABLED_LinkManagerAddTwiceCancelTwice
+#else
+#define MAYBE_LinkManagerAddTwiceCancelTwice LinkManagerAddTwiceCancelTwice
+#endif
+TEST_F(PrerenderTest, MAYBE_LinkManagerAddTwiceCancelTwice) {
   SetConcurrency(2);
   EXPECT_TRUE(IsEmptyPrerenderLinkManager());
   GURL url("http://www.myexample.com");
@@ -1567,7 +1574,15 @@ TEST_F(PrerenderTest, LinkManagerAddTwiceCancelTwice) {
 
 // TODO(gavinp): Update this test after abandon has an effect on Prerenders,
 // like shortening the timeouts.
-TEST_F(PrerenderTest, LinkManagerAddTwiceAbandonTwiceUseTwice) {
+// Flaky on Android, crbug.com/1087876.
+#if defined(OS_ANDROID)
+#define MAYBE_LinkManagerAddTwiceAbandonTwiceUseTwice \
+  DISABLED_LinkManagerAddTwiceAbandonTwiceUseTwice
+#else
+#define MAYBE_LinkManagerAddTwiceAbandonTwiceUseTwice \
+  LinkManagerAddTwiceAbandonTwiceUseTwice
+#endif
+TEST_F(PrerenderTest, MAYBE_LinkManagerAddTwiceAbandonTwiceUseTwice) {
   SetConcurrency(2);
   EXPECT_TRUE(IsEmptyPrerenderLinkManager());
   GURL url("http://www.myexample.com");