Prevent duplicate content script injection defined in manifest.json

chrome/browser/extensions/content_script_apitest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stddef.h>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
@@ skipping 317 matching lines @@
     // could lead to spoofing). Unfortunately, host_resolver seems to have
     // problems with redirecting "chrome.google.com" to the test server, so we
     // can't use the real Webstore's URL. If this changes, we could clean this
     // up.
     command_line->AppendSwitchASCII(
         switches::kAppsGalleryURL,
         base::StringPrintf("http://%s", kWebstoreDomain));
   }
 };
 
+IN_PROC_BROWSER_TEST_F(ExtensionApiTest,

[Devlin, 2016/07/11 23:45:50]

Though we don't do it uniformly, I think a comment at the top of the test (or
comments sprinkled throughout, but that's probably overkill here) is useful for
quickly understanding the purpose.  So in this case, just something like:
// Test that a script that matches two separate match patterns is only
// injected once.

[catmullings, 2016/07/12 22:23:26]

Done.

[catmullings, 2016/07/12 22:23:26]

Thanks Devlin. I like the comment you've written. :) 
I will use that here.

+                       ContentScriptDuplicateScriptInjection) {
+  host_resolver()->AddRule("maps.google.com", "127.0.0.1");
+  ASSERT_TRUE(StartEmbeddedTestServer());
+
+  std::string port_string = base::UintToString(embedded_test_server()->port());
+  GURL url = GURL("http://maps.google.com:"

[Devlin, 2016/07/11 23:45:50]

We have handy utility called base::StringPrintf, which would clean this up a
little bit.

[catmullings, 2016/07/12 22:23:26]

Done.

+                   + port_string
+                   + "/extensions/test_file.html");
+
+  ASSERT_TRUE(LoadExtension(
+    test_data_dir_.AppendASCII("content_scripts/duplicate_script_injection")));

[Devlin, 2016/07/11 23:45:50]

the indentation here is off (feel free to just run git cl format, which should
catch these).

[catmullings, 2016/07/12 22:23:26]

Done.

+
+  ui_test_utils::NavigateToURL(browser(), url);
+
+  bool scripts_injected_once;

[Devlin, 2016/07/11 23:45:50]

All variables should be initialized at creation.

[catmullings, 2016/07/12 22:23:26]

Done.

[catmullings, 2016/07/12 22:23:26]

Many variables in this file are left uninitialized, so I was following that
style.
Though I'll it a practice to initialize variables at creation. 

[Devlin, 2016/07/12 23:32:36]

I can't find any examples of uninitialized variables from a quick skim, but if
there are some, they should be fixed. :)

Note that this is only relevant for POD variables, since anything with a CTOR is
automatically initialized via RAII.

+  ASSERT_TRUE(content::ExecuteScriptAndExtractBool(
+      browser()->tab_strip_model()->GetActiveWebContents(),
+      "window.domAutomationController.send("
+      "document.getElementsByClassName('test-duplicate-script-injection')"
+      ".length == 1)",
+      &scripts_injected_once));
+  ASSERT_TRUE(scripts_injected_once);
+}
+
 IN_PROC_BROWSER_TEST_F(ContentScriptCssInjectionTest,
                        ContentScriptInjectsStyles) {
   ASSERT_TRUE(StartEmbeddedTestServer());
   host_resolver()->AddRule(kWebstoreDomain, "127.0.0.1");
 
   ASSERT_TRUE(LoadExtension(test_data_dir_.AppendASCII("content_scripts")
                                           .AppendASCII("css_injection")));
 
   // CSS injection should be allowed on an aribitrary web page.
   GURL url =
@@ skipping 281 matching lines @@
   ExtensionTestMessageListener iframe_loaded_listener("iframe loaded", false);
   ExtensionTestMessageListener content_script_listener("script injected",
                                                        false);
   LoadExtension(data_dir.AppendASCII("script_a_com"));
   LoadExtension(data_dir.AppendASCII("background_page_iframe"));
   iframe_loaded_listener.WaitUntilSatisfied();
   EXPECT_FALSE(content_script_listener.was_satisfied());
 }
 
 }  // namespace extensions