Blimp: Add BlobChannel Helium messages and delegate impls.

blimp/net/test_common.h

Index: blimp/net/test_common.h
diff --git a/blimp/net/test_common.h b/blimp/net/test_common.h
index 5aaae7eee0a4ca44246d37994afb85b5358fa6aa..c726feba5a8c2645cf72d5f2d4e59f95fba64786 100644
--- a/blimp/net/test_common.h
+++ b/blimp/net/test_common.h
@@ -60,6 +60,11 @@ MATCHER_P(BufferEqualsProto, message, "") {
   return expected_serialized == actual_serialized;
 }
 
+// Checks if the contents of a BlobDataPtr match the string |expected|.
+MATCHER_P(BlobDataPtrEqualsString, expected, "") {
+  return expected == arg->data;
+}
+
 // GMock action that writes data from a string to an IOBuffer.
 //
 //   buf_idx (template parameter 0): 0-based index of the IOBuffer arg.