Fix InstallServiceWorkItemTest deletes Chrome key under ClientState.

Greg discovered that InstallServiceWorkItemTest.Do_ServiceName will
create Google\Update\ClientState\{8A69D345-D564-463c-AFF1-A69D9E530F96}
if it does not exist and then delete it. If the test is run on a
development machine, it will corrupt the stable Chrome install.

Bug: 1057233
Change-Id: I5e71c6ab9776f376dcffe0a415bfb084baec8e26
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2086353
Auto-Submit: S. Ganesh <ganesh@chromium.org>
Reviewed-by: Greg Thompson <grt@chromium.org>
Commit-Queue: Greg Thompson <grt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#746738}

chrome/installer/util/install_service_work_item_unittest.cc

@@ -154,7 +154,7 @@ TEST_F(InstallServiceWorkItemTest, Do_ServiceName) {
   EXPECT_EQ(0UL,
             GetImpl(item.get())->GetCurrentServiceName().find(kServiceName));
 
-  EXPECT_EQ(ERROR_SUCCESS, key.DeleteKey(L""));
+  EXPECT_EQ(ERROR_SUCCESS, key.DeleteValue(kServiceName));
 }
 
 }  // namespace installer