Don't use dtls1_read_bytes to read messages.

This was probably the worst offender of them all as read_bytes is the wrong
abstraction to begin with. Note this is a slight change in how processing a
record works. Rather than reading one fragment at a time, we process all
fragments in a record and return. The intent here is so that all records are
processed atomically since the connection eventually will not be able to retain
a buffer holding the record.

This loses a ton of (though not quite all yet) those a2b macros.

Change-Id: Ibe4bbcc33c496328de08d272457d2282c411b38b
Reviewed-on: https://boringssl-review.googlesource.com/8176
Reviewed-by: David Benjamin <davidben@google.com>
diff --git a/ssl/test/runner/runner.go b/ssl/test/runner/runner.go
index 1b0bf54..71d14d2 100644
--- a/ssl/test/runner/runner.go
+++ b/ssl/test/runner/runner.go
@@ -1772,7 +1772,7 @@
 				},
 			},
 			shouldFail:    true,
-			expectedError: ":UNEXPECTED_MESSAGE:",
+			expectedError: ":BAD_HANDSHAKE_RECORD:",
 		},
 		{
 			protocol: dtls,
@@ -1783,7 +1783,7 @@
 				},
 			},
 			shouldFail:    true,
-			expectedError: ":EXCESSIVE_MESSAGE_SIZE:",
+			expectedError: ":BAD_HANDSHAKE_RECORD:",
 		},
 		{
 			protocol: dtls,
@@ -1794,7 +1794,7 @@
 				},
 			},
 			shouldFail:    true,
-			expectedError: ":EXCESSIVE_MESSAGE_SIZE:",
+			expectedError: ":BAD_HANDSHAKE_RECORD:",
 		},
 		{
 			protocol: dtls,