Add support for writing unit tests for Mojo-backed apps/extensions APIs.

extensions/test/test_extensions_client.cc

Index: extensions/test/test_extensions_client.cc
diff --git a/extensions/test/test_extensions_client.cc b/extensions/test/test_extensions_client.cc
index 8cee49a19c25046dd71f08138847451721b42cb9..c9406c809ac918c0deba5b8eb987fae8cdf9e059 100644
--- a/extensions/test/test_extensions_client.cc
+++ b/extensions/test/test_extensions_client.cc
@@ -4,6 +4,7 @@
 
 #include "extensions/test/test_extensions_client.h"
 
+#include "extensions/common/api/generated_schemas.h"
 #include "extensions/common/common_manifest_handlers.h"
 #include "extensions/common/features/feature_provider.h"
 #include "extensions/common/features/json_feature_provider_source.h"
@@ -77,12 +78,12 @@ bool TestExtensionsClient::IsScriptableURL(const GURL& url,
 
 bool TestExtensionsClient::IsAPISchemaGenerated(
     const std::string& name) const {
-  return false;
+  return core_api::GeneratedSchemas::IsGenerated(name);
 }
 
 base::StringPiece TestExtensionsClient::GetAPISchema(
     const std::string& name) const {
-  return base::StringPiece();
+  return core_api::GeneratedSchemas::Get(name);
 }
 
 void TestExtensionsClient::RegisterAPISchemaResources(ExtensionAPI* api) const {