Prevent duplicate content script injection defined in manifest.json

extensions/renderer/user_script_injector.cc

 // Copyright 2014 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 "extensions/renderer/user_script_injector.h"
 
 #include <tuple>
 #include <vector>
 
 #include "base/lazy_instance.h"
@@ skipping 179 matching lines @@
       web_frame, web_frame->document().url(), script_->match_about_blank());
 
   return injection_host->CanExecuteOnFrame(
       effective_document_url,
       content::RenderFrame::FromWebFrame(web_frame),
       tab_id,
       is_declarative_);
 }
 
 std::vector<blink::WebScriptSource> UserScriptInjector::GetJsSources(
-    UserScript::RunLocation run_location) const {
+    UserScript::RunLocation run_location,
+    ScriptsRunInfo* scripts_run_info) const {
   std::vector<blink::WebScriptSource> sources;
   if (!script_)
     return sources;
 
   DCHECK_EQ(script_->run_location(), run_location);
 
   const UserScript::FileList& js_scripts = script_->js_scripts();
 
   for (UserScript::FileList::const_iterator iter = js_scripts.begin();
        iter != js_scripts.end();
        ++iter) {
+    const GURL& script_url = iter->url();
+    // Check if the script is already injected.
+    if (scripts_run_info->injected_scripts.count(script_url) != 0)
+      continue;
+
     std::string content = iter->GetContent().as_string();
 
     // We add this dumb function wrapper for user scripts to emulate what
     // Greasemonkey does.
     if (script_->emulate_greasemonkey()) {
       content.insert(0, kUserScriptHead);
       content += kUserScriptTail;
     }
     sources.push_back(blink::WebScriptSource(
-        blink::WebString::fromUTF8(content), iter->url()));
+        blink::WebString::fromUTF8(content), script_url));
+
+    scripts_run_info->injected_scripts.insert(script_url);
   }
 
   // Emulate Greasemonkey API for scripts that were converted to extension
   // user scripts.
   if (script_->emulate_greasemonkey())
     sources.insert(sources.begin(), g_greasemonkey_api.Get().GetSource());
 
   return sources;
 }
 
 std::vector<std::string> UserScriptInjector::GetCssSources(
-    UserScript::RunLocation run_location) const {
+    UserScript::RunLocation run_location,
+    ScriptsRunInfo* scripts_run_info) const {
   DCHECK_EQ(UserScript::DOCUMENT_START, run_location);
 
   std::vector<std::string> sources;
   if (!script_)
     return sources;
 
   const UserScript::FileList& css_scripts = script_->css_scripts();
+
   for (UserScript::FileList::const_iterator iter = css_scripts.begin();
        iter != css_scripts.end();
        ++iter) {
-    sources.push_back(iter->GetContent().as_string());
+    GURL scriptUrl = iter->url();
+    // Check if the script is already injected
+    if (scripts_run_info->injected_scripts.find(scriptUrl) ==
+        scripts_run_info->injected_scripts.end()) {
+      std::string content = iter->GetContent().as_string();

[Devlin, 2016/07/13 18:58:36]

is this variable ever used?

[catmullings, 2016/07/15 20:26:59]

Nope. I had set it up to pass it as a parameter to the following .push_back()
call, but I ended up doing it inline below.

[catmullings, 2016/07/15 20:26:59]

Done.

+      sources.push_back(iter->GetContent().as_string());
+
+      scripts_run_info->injected_scripts.insert(scriptUrl);
+    }
   }
   return sources;
 }
 
 void UserScriptInjector::GetRunInfo(
     ScriptsRunInfo* scripts_run_info,
     UserScript::RunLocation run_location) const {
   if (!script_)
     return;
 
@@ skipping 15 matching lines @@
 void UserScriptInjector::OnInjectionComplete(
     std::unique_ptr<base::Value> execution_result,
     UserScript::RunLocation run_location,
     content::RenderFrame* render_frame) {}
 
 void UserScriptInjector::OnWillNotInject(InjectFailureReason reason,
                                          content::RenderFrame* render_frame) {
 }
 
 }  // namespace extensions