Reimplement gpu message bus for invalidated bitmap gen IDs

Review URL: https://codereview.chromium.org/902873002
diff --git a/tests/MessageBusTest.cpp b/tests/MessageBusTest.cpp
index f7a02b2..163addf 100644
--- a/tests/MessageBusTest.cpp
+++ b/tests/MessageBusTest.cpp
@@ -25,7 +25,7 @@
     SkMessageBus<TestMessage>::Post(m2);
 
     // Make sure we got two.
-    SkTDArray<TestMessage> messages;
+    SkTArray<TestMessage> messages;
     inbox1.poll(&messages);
     REPORTER_ASSERT(r, 2 == messages.count());
     REPORTER_ASSERT(r, 5 == messages[0].x);