ScopedGeneric: delete regex in death tests.

The official builds apparently doesn't print the error message from
CHECK failure, so delete the death test regexes. While we're at it,
switch from the ifdef to EXPECT_DEATH_IF_SUPPORTED.

TBR=dcheng@chromium.org

Bug: 900764
Change-Id: I61448b5fcb903b35a4cc01e0eb599ba35be1d402
Reviewed-on: https://chromium-review.googlesource.com/c/1311838Reviewed-by: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Commit-Queue: Josh Gao <jmgao@google.com>
Cr-Commit-Position: refs/heads/master@{#604468}

base/scoped_generic_unittest.cc

@@ -164,14 +164,11 @@ TEST(ScopedGenericTest, Receive) {
 
   EXPECT_EQ(456, a->get());
 
-#if !defined(OS_IOS)
-  // Death tests are unsupported on iOS.
   {
     ScopedInt::Receiver r(*a);
-    EXPECT_DEATH(a.reset(), "destroyed with active receiver");
-    EXPECT_DEATH(ScopedInt::Receiver(*a).get(), "existing Receiver");
+    EXPECT_DEATH_IF_SUPPORTED(a.reset(), "");
+    EXPECT_DEATH_IF_SUPPORTED(ScopedInt::Receiver(*a).get(), "");
   }
-#endif
 }
 
 namespace {