Revert of 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 f371f2a33010d7b712017a679f8884a28af86f00..4521f8037ed2d44c3c1c67c5b96ea828b1fb5988 100644
--- a/mojo/edk/embedder/embedder_unittest.cc
+++ b/mojo/edk/embedder/embedder_unittest.cc
@@ -224,15 +224,7 @@
                                      nullptr));
 }
 
-#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) {
+TEST_F(EmbedderTest, PipeSetup_LaunchFailure) {
   PlatformChannelPair pair;
 
   std::string child_token = GenerateRandomToken();