Remove FlatbufferString

FlatbufferSpan does most of the same things, with stronger typing and
more flexibility.

Change-Id: I8aec46d05be6db9395a47b260b7413b0f1b247e6
diff --git a/aos/testing/flatbuffer_eq.h b/aos/testing/flatbuffer_eq.h
index b6b93d9..c4b708b 100644
--- a/aos/testing/flatbuffer_eq.h
+++ b/aos/testing/flatbuffer_eq.h
@@ -51,7 +51,7 @@
 template <typename T>
 class FlatbufferEqMatcher : public ::testing::MatcherInterface<const T *> {
  public:
-  FlatbufferEqMatcher(aos::FlatbufferString<T> expected)
+  FlatbufferEqMatcher(aos::FlatbufferSpan<T> expected)
       : expected_(std::move(expected)) {}
   ~FlatbufferEqMatcher() override = default;
 
@@ -70,7 +70,7 @@
   }
 
  private:
-  const aos::FlatbufferString<T> expected_;
+  const aos::FlatbufferSpan<T> expected_;
 };
 
 // Returns a googlemock matcher which will compare a `const T *` or a `const
@@ -81,7 +81,7 @@
 template <typename T>
 inline auto FlatbufferEq(const aos::NonSizePrefixedFlatbuffer<T> &expected) {
   return FlatbufferUnwrapped(::testing::MakeMatcher(
-      new FlatbufferEqMatcher(aos::FlatbufferString<T>(expected))));
+      new FlatbufferEqMatcher(aos::FlatbufferSpan<T>(expected))));
 }
 
 }  // namespace testing