Enable standalone/io/http_test, splitting it into three separate tests.

tests/standalone/standalone.status

Index: tests/standalone/standalone.status
diff --git a/tests/standalone/standalone.status b/tests/standalone/standalone.status
index ca1cdbaf4b7437aa2220a11016082ad9d86a82e2..a67d62dd28b4d2b26506b0547e7232cd3de95bc5 100644
--- a/tests/standalone/standalone.status
+++ b/tests/standalone/standalone.status
@@ -6,8 +6,6 @@ out_of_memory_test: Skip # Issue 2345
 
 package/invalid_uri_test: Fail, OK # Fails intentionally
 
-io/http_test: Pass, Fail  # Issue 2987
-
 [ $runtime == vm && $checked ]
 # These tests have type errors on purpose.
 io/process_invalid_arguments_test: Fail, OK
@@ -77,5 +75,5 @@ io/options_test: Fail
 *: Skip
 
 [$compiler == dart2js && $checked ]
-io/http_test: Skip # Timeout TODO(ngeoffray): investigate
+io/http_read_test: Skip # Timeout TODO(ngeoffray): investigate
 io/list_input_stream_test: Skip # Timeout TODO(ngeoffray): investigate