Don't access WebPluginInfo array out of bounds in PluginGroup::RemovePlugin.

webkit/plugins/npapi/plugin_group_unittest.cc

Index: webkit/plugins/npapi/plugin_group_unittest.cc
diff --git a/webkit/plugins/npapi/plugin_group_unittest.cc b/webkit/plugins/npapi/plugin_group_unittest.cc
index 9c2d137a327f3bd4ef255d3f13fc067e11757a00..28f8fe60f401a3489b52e192d2066749ae6f753d 100644
--- a/webkit/plugins/npapi/plugin_group_unittest.cc
+++ b/webkit/plugins/npapi/plugin_group_unittest.cc
@@ -286,6 +286,10 @@ TEST(PluginGroupTest, MultipleVersions) {
   EXPECT_TRUE(group->RemovePlugin(kPlugin3044.path));
   EXPECT_EQ(kPlugin3043.desc, group->description());
   EXPECT_TRUE(group->IsVulnerable());
+
+  EXPECT_TRUE(group->RemovePlugin(kPlugin3043.path));
+  EXPECT_TRUE(group->IsEmpty());
+  EXPECT_EQ(string16(), group->description());
 }
 
 }  // namespace npapi