Change ComponentLoader::AddOrReplace to return an empty string on failure.

chrome/browser/extensions/component_loader_unittest.cc

Index: chrome/browser/extensions/component_loader_unittest.cc
diff --git a/chrome/browser/extensions/component_loader_unittest.cc b/chrome/browser/extensions/component_loader_unittest.cc
index ef61a0b973bc01dbda4c80744423c5bc1b6606a7..c047031ad7bf7a507b2065bebb4df296aa380666 100644
--- a/chrome/browser/extensions/component_loader_unittest.cc
+++ b/chrome/browser/extensions/component_loader_unittest.cc
@@ -292,6 +292,7 @@ TEST_F(ComponentLoaderTest, AddOrReplace) {
   base::FilePath known_extension = GetBasePath()
       .AppendASCII("override_component_extension");
   base::FilePath unknow_extension = extension_path_;
+  base::FilePath invalid_extension = GetBasePath().AppendASCII("bad");
 
   // Replace a default component extension.
   component_loader_.AddOrReplace(known_extension);
@@ -313,6 +314,10 @@ TEST_F(ComponentLoaderTest, AddOrReplace) {
   component_loader_.AddOrReplace(known_extension);
   EXPECT_EQ(default_count + 1, extension_service_.extensions()->size());
   EXPECT_EQ(1u, extension_service_.unloaded_count());
+
+  // Add an invalid component extension.
+  std::string extension_id = component_loader_.AddOrReplace(invalid_extension);
+  EXPECT_TRUE(extension_id.empty());
 }
 
 }  // namespace extensions