Disable two tests in mojo_system_unittests that are suspected to be timing out

mojo/edk/embedder/embedder_unittest.cc

Index: mojo/edk/embedder/embedder_unittest.cc
diff --git a/mojo/edk/embedder/embedder_unittest.cc b/mojo/edk/embedder/embedder_unittest.cc
index 4521f8037ed2d44c3c1c67c5b96ea828b1fb5988..f371f2a33010d7b712017a679f8884a28af86f00 100644
--- a/mojo/edk/embedder/embedder_unittest.cc
+++ b/mojo/edk/embedder/embedder_unittest.cc
@@ -224,7 +224,15 @@ TEST_F(EmbedderTest, PipeSetup_LaunchDeath) {
                                      nullptr));
 }
 
-TEST_F(EmbedderTest, PipeSetup_LaunchFailure) {
+#if defined(OS_ANDROID)
+// This test is suspected to be flaky on android https://crbug.com/663998.
+#define MAYBE_PipeSetup_LaunchFailure \
+    DISABLED_PipeSetup_LaunchFailure
+#else
+#define MAYBE_PipeSetup_LaunchFailure \
+    PipeSetup_LaunchFailure
+#endif
+TEST_F(EmbedderTest, MAYBE_PipeSetup_LaunchFailure) {
   PlatformChannelPair pair;
 
   std::string child_token = GenerateRandomToken();