Introduce ScriptInjection in extensions/renderer to inject UserScripts

UserScriptSlave was responsible for too much, and the logic was getting
cluttered (which also made changes in, e.g.
https://codereview.chromium.org/288053002/ difficult to read, write, and
review). Refactor the logic to inject the scripts into a new class, so that
UserScriptSlave is pretty much just responsible for containing them.

BUG=373961

Review URL: https://codereview.chromium.org/284153006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271532 0039d316-1c4b-4281-b951-d872f2087c98

5 files changed, 415 insertions, 186 deletions

diff --git a/extensions/renderer/script_injection.cc b/extensions/renderer/script_injection.cc
new file mode 100644
index 0000000..4db534a
--- /dev/null
+++ b/extensions/renderer/script_injection.cc
@@ -0,0 +1,202 @@
+// 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/script_injection.h"
+
+#include <vector>
+
+#include "base/lazy_instance.h"
+#include "base/metrics/histogram.h"
+#include "content/public/common/url_constants.h"
+#include "extensions/common/extension.h"
+#include "extensions/common/extension_messages.h"
+#include "extensions/common/permissions/permissions_data.h"
+#include "extensions/renderer/dom_activity_logger.h"
+#include "extensions/renderer/extension_groups.h"
+#include "extensions/renderer/script_context.h"
+#include "extensions/renderer/user_script_slave.h"
+#include "grit/renderer_resources.h"
+#include "third_party/WebKit/public/web/WebDocument.h"
+#include "third_party/WebKit/public/web/WebFrame.h"
+#include "third_party/WebKit/public/web/WebScriptSource.h"
+#include "ui/base/resource/resource_bundle.h"
+#include "url/gurl.h"
+
+namespace extensions {
+
+namespace {
+
+// These two strings are injected before and after the Greasemonkey API and
+// user script to wrap it in an anonymous scope.
+const char kUserScriptHead[] = "(function (unsafeWindow) {\n";
+const char kUserScriptTail[] = "\n})(window);";
+
+// Greasemonkey API source that is injected with the scripts.
+struct GreasemonkeyApiJsString {
+  GreasemonkeyApiJsString();
+  blink::WebScriptSource source;
+};
+
+// The below constructor, monstrous as it is, just makes a WebScriptSource from
+// the GreasemonkeyApiJs resource.
+GreasemonkeyApiJsString::GreasemonkeyApiJsString()
+    : source(blink::WebScriptSource(blink::WebString::fromUTF8(
+          ResourceBundle::GetSharedInstance().GetRawDataResource(
+              IDR_GREASEMONKEY_API_JS).as_string()))) {
+}
+
+base::LazyInstance<GreasemonkeyApiJsString> g_greasemonkey_api =
+    LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
+ScriptInjection::ScriptsRunInfo::ScriptsRunInfo() : num_css(0u), num_js(0u) {
+}
+
+ScriptInjection::ScriptsRunInfo::~ScriptsRunInfo() {
+}
+
+// static
+GURL ScriptInjection::GetDocumentUrlForFrame(blink::WebFrame* frame) {
+  GURL data_source_url = ScriptContext::GetDataSourceURLForFrame(frame);
+  if (!data_source_url.is_empty() && frame->isViewSourceModeEnabled()) {
+    data_source_url = GURL(content::kViewSourceScheme + std::string(":") +
+                           data_source_url.spec());
+  }
+
+  return data_source_url;
+}
+
+ScriptInjection::ScriptInjection(
+    scoped_ptr<UserScript> script,
+    UserScriptSlave* user_script_slave)
+    : script_(script.Pass()),
+      extension_id_(script_->extension_id()),
+      user_script_slave_(user_script_slave),
+      is_standalone_or_emulate_greasemonkey_(
+          script_->is_standalone() || script_->emulate_greasemonkey()) {
+}
+
+ScriptInjection::~ScriptInjection() {
+}
+
+bool ScriptInjection::WantsToRun(blink::WebFrame* frame,
+                                 UserScript::RunLocation run_location,
+                                 const GURL& document_url) const {
+  if (frame->parent() && !script_->match_all_frames())
+    return false;  // Only match subframes if the script declared it wanted to.
+
+  const Extension* extension = user_script_slave_->GetExtension(extension_id_);
+  // Since extension info is sent separately from user script info, they can
+  // be out of sync. We just ignore this situation.
+  if (!extension)
+    return false;
+
+  // Content scripts are not tab-specific.
+  static const int kNoTabId = -1;
+  // We don't have a process id in this context.
+  static const int kNoProcessId = -1;
+
+  GURL effective_document_url = ScriptContext::GetEffectiveDocumentURL(
+      frame, document_url, script_->match_about_blank());
+
+  if (!PermissionsData::CanExecuteScriptOnPage(extension,
+                                               effective_document_url,
+                                               frame->top()->document().url(),
+                                               kNoTabId,
+                                               script_.get(),
+                                               kNoProcessId,
+                                               NULL /* ignore error */)) {
+    return false;
+  }
+
+  return ShouldInjectCSS(run_location) || ShouldInjectJS(run_location);
+}
+
+void ScriptInjection::Inject(blink::WebFrame* frame,
+                             UserScript::RunLocation run_location,
+                             ScriptsRunInfo* scripts_run_info) const {
+  DCHECK(frame);
+  DCHECK(scripts_run_info);
+  DCHECK(WantsToRun(frame, run_location, GetDocumentUrlForFrame(frame)));
+  DCHECK(user_script_slave_->GetExtension(extension_id_));
+
+  if (ShouldInjectCSS(run_location))
+    InjectCSS(frame, scripts_run_info);
+  if (ShouldInjectJS(run_location))
+    InjectJS(frame, scripts_run_info);
+}
+
+bool ScriptInjection::ShouldInjectJS(UserScript::RunLocation run_location)
+    const {
+  return !script_->js_scripts().empty() &&
+         script_->run_location() == run_location;
+}
+
+bool ScriptInjection::ShouldInjectCSS(UserScript::RunLocation run_location)
+    const {
+  return !script_->css_scripts().empty() &&
+         run_location == UserScript::DOCUMENT_START;
+}
+
+void ScriptInjection::InjectJS(blink::WebFrame* frame,
+                               ScriptsRunInfo* scripts_run_info) const {
+  const UserScript::FileList& js_scripts = script_->js_scripts();
+  std::vector<blink::WebScriptSource> sources;
+  scripts_run_info->num_js += js_scripts.size();
+  for (UserScript::FileList::const_iterator iter = js_scripts.begin();
+       iter != js_scripts.end();
+       ++iter) {
+    std::string content = iter->GetContent().as_string();
+
+    // We add this dumb function wrapper for standalone user script to
+    // emulate what Greasemonkey does.
+    // TODO(aa): I think that maybe "is_standalone" scripts don't exist
+    // anymore. Investigate.
+    if (is_standalone_or_emulate_greasemonkey_) {
+      content.insert(0, kUserScriptHead);
+      content += kUserScriptTail;
+    }
+    sources.push_back(blink::WebScriptSource(
+        blink::WebString::fromUTF8(content), iter->url()));
+  }
+
+  // Emulate Greasemonkey API for scripts that were converted to extensions
+  // and "standalone" user scripts.
+  if (is_standalone_or_emulate_greasemonkey_)
+    sources.insert(sources.begin(), g_greasemonkey_api.Get().source);
+
+  int isolated_world_id =
+      user_script_slave_->GetIsolatedWorldIdForExtension(
+          user_script_slave_->GetExtension(extension_id_), frame);
+  base::ElapsedTimer exec_timer;
+  DOMActivityLogger::AttachToWorld(isolated_world_id, extension_id_);
+  frame->executeScriptInIsolatedWorld(isolated_world_id,
+                                      &sources.front(),
+                                      sources.size(),
+                                      EXTENSION_GROUP_CONTENT_SCRIPTS);
+  UMA_HISTOGRAM_TIMES("Extensions.InjectScriptTime", exec_timer.Elapsed());
+
+  for (std::vector<blink::WebScriptSource>::const_iterator iter =
+           sources.begin();
+       iter != sources.end();
+       ++iter) {
+    scripts_run_info->executing_scripts[extension_id_].insert(
+        GURL(iter->url).path());
+  }
+}
+
+void ScriptInjection::InjectCSS(blink::WebFrame* frame,
+                                ScriptsRunInfo* scripts_run_info) const {
+  const UserScript::FileList& css_scripts = script_->css_scripts();
+  scripts_run_info->num_css += css_scripts.size();
+  for (UserScript::FileList::const_iterator iter = css_scripts.begin();
+       iter != css_scripts.end();
+       ++iter) {
+    frame->document().insertStyleSheet(
+        blink::WebString::fromUTF8(iter->GetContent().as_string()));
+  }
+}
+
+}  // namespace extensions
diff --git a/extensions/renderer/script_injection.h b/extensions/renderer/script_injection.h
new file mode 100644
index 0000000..813fbb4
--- /dev/null
+++ b/extensions/renderer/script_injection.h
@@ -0,0 +1,107 @@
+// 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.
+
+#ifndef EXTENSIONS_RENDERER_SCRIPT_INJECTION_H_
+#define EXTENSIONS_RENDERER_SCRIPT_INJECTION_H_
+
+#include <map>
+#include <set>
+#include <string>
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/timer/elapsed_timer.h"
+#include "extensions/common/user_script.h"
+
+class GURL;
+
+namespace blink {
+class WebFrame;
+}
+
+namespace extensions {
+class UserScriptSlave;
+
+// This class is a wrapper around a UserScript that knows how to inject itself
+// into a frame.
+class ScriptInjection {
+ public:
+  // Map of extensions IDs to the executing script paths.
+  typedef std::map<std::string, std::set<std::string> > ExecutingScriptsMap;
+
+  // A struct containing information about a script run.
+  struct ScriptsRunInfo {
+    ScriptsRunInfo();
+    ~ScriptsRunInfo();
+
+    // The number of CSS scripts injected.
+    size_t num_css;
+    // The number of JS scripts injected.
+    size_t num_js;
+    // A map of extension ids to executing script paths.
+    ExecutingScriptsMap executing_scripts;
+    // The elapsed time since the ScriptsRunInfo was constructed.
+    base::ElapsedTimer timer;
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(ScriptsRunInfo);
+  };
+
+  // Return the URL to use as the document url when checking permissions for
+  // script injection.
+  static GURL GetDocumentUrlForFrame(blink::WebFrame* frame);
+
+  ScriptInjection(scoped_ptr<UserScript> script,
+                  UserScriptSlave* user_script_slave);
+  ~ScriptInjection();
+
+  // Returns true if this ScriptInjection wants to run on the given |frame| at
+  // the given |run_location| (i.e., if this script would inject either JS or
+  // CSS).
+  bool WantsToRun(blink::WebFrame* frame,
+                  UserScript::RunLocation run_location,
+                  const GURL& document_url) const;
+
+  // Injects the script into the given |frame|, and updates |scripts_run_info|
+  // information about the run.
+  void Inject(blink::WebFrame* frame,
+              UserScript::RunLocation run_location,
+              ScriptsRunInfo* scripts_run_info) const;
+
+  const std::string& extension_id() { return extension_id_; }
+
+ private:
+  // Returns true if the script will inject [css|js] at the given
+  // |run_location|.
+  bool ShouldInjectJS(UserScript::RunLocation run_location) const;
+  bool ShouldInjectCSS(UserScript::RunLocation run_location) const;
+
+  // Injects the [css|js] scripts into the frame, and stores the results of
+  // the run in |scripts_run_info|.
+  void InjectJS(blink::WebFrame* frame, ScriptsRunInfo* scripts_run_info) const;
+  void InjectCSS(blink::WebFrame* frame, ScriptsRunInfo* scripts_run_info)
+      const;
+
+  // The UserScript this is injecting.
+  scoped_ptr<UserScript> script_;
+
+  // The associated extension's id. This is a safe const&, since it is owned by
+  // the |user_script_|.
+  const std::string& extension_id_;
+
+  // The associated UserScriptSlave.
+  // It's unfortunate that this is needed, but we use it to get the isolated
+  // world ids and the associated extensions.
+  // TODO(rdevlin.cronin): It would be nice to clean this up more.
+  UserScriptSlave* user_script_slave_;
+
+  // True if the script is a standalone script or emulates greasemonkey.
+  bool is_standalone_or_emulate_greasemonkey_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScriptInjection);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_RENDERER_SCRIPT_INJECTION_H_
diff --git a/extensions/renderer/user_script_scheduler.cc b/extensions/renderer/user_script_scheduler.cc
index 92918d0..cc0d84b 100644
--- a/extensions/renderer/user_script_scheduler.cc
+++ b/extensions/renderer/user_script_scheduler.cc
@@ -24,6 +24,7 @@
 #include "third_party/WebKit/public/web/WebDocument.h"
 #include "third_party/WebKit/public/web/WebFrame.h"
 #include "third_party/WebKit/public/web/WebScopedUserGesture.h"
+#include "third_party/WebKit/public/web/WebScriptSource.h"
 #include "third_party/WebKit/public/web/WebView.h"
 #include "v8/include/v8.h"
 
@@ -210,7 +211,8 @@ void UserScriptScheduler::ExecuteCodeImpl(
     }
 
     if (params.is_javascript) {
-      WebScriptSource source(WebString::fromUTF8(params.code), params.file_url);
+      blink::WebScriptSource source(
+          WebString::fromUTF8(params.code), params.file_url);
       v8::HandleScope scope(v8::Isolate::GetCurrent());
 
       scoped_ptr<content::V8ValueConverter> v8_converter(
@@ -223,7 +225,7 @@ void UserScriptScheduler::ExecuteCodeImpl(
         script_value = child_frame->executeScriptAndReturnValue(source);
       } else {
         blink::WebVector<v8::Local<v8::Value> > results;
-        std::vector<WebScriptSource> sources;
+        std::vector<blink::WebScriptSource> sources;
         sources.push_back(source);
         int isolated_world_id =
             dispatcher_->user_script_slave()->GetIsolatedWorldIdForExtension(
diff --git a/extensions/renderer/user_script_slave.cc b/extensions/renderer/user_script_slave.cc
index 8e176ef..036581b 100644
--- a/extensions/renderer/user_script_slave.cc
+++ b/extensions/renderer/user_script_slave.cc
@@ -6,14 +6,11 @@
 
 #include <map>
 
-#include "base/command_line.h"
 #include "base/logging.h"
 #include "base/memory/shared_memory.h"
 #include "base/metrics/histogram.h"
 #include "base/pickle.h"
-#include "base/strings/stringprintf.h"
 #include "base/timer/elapsed_timer.h"
-#include "content/public/common/url_constants.h"
 #include "content/public/renderer/render_thread.h"
 #include "content/public/renderer/render_view.h"
 #include "extensions/common/extension.h"
@@ -21,66 +18,48 @@
 #include "extensions/common/extension_set.h"
 #include "extensions/common/manifest_handlers/csp_info.h"
 #include "extensions/common/permissions/permissions_data.h"
-#include "extensions/renderer/dom_activity_logger.h"
-#include "extensions/renderer/extension_groups.h"
 #include "extensions/renderer/extensions_renderer_client.h"
 #include "extensions/renderer/script_context.h"
-#include "grit/renderer_resources.h"
-#include "third_party/WebKit/public/platform/WebURLRequest.h"
-#include "third_party/WebKit/public/platform/WebVector.h"
-#include "third_party/WebKit/public/web/WebDocument.h"
 #include "third_party/WebKit/public/web/WebFrame.h"
 #include "third_party/WebKit/public/web/WebSecurityOrigin.h"
 #include "third_party/WebKit/public/web/WebSecurityPolicy.h"
 #include "third_party/WebKit/public/web/WebView.h"
-#include "ui/base/resource/resource_bundle.h"
 #include "url/gurl.h"
 
 using blink::WebFrame;
 using blink::WebSecurityOrigin;
 using blink::WebSecurityPolicy;
 using blink::WebString;
-using blink::WebVector;
 using blink::WebView;
 using content::RenderThread;
 
 namespace extensions {
 
-// These two strings are injected before and after the Greasemonkey API and
-// user script to wrap it in an anonymous scope.
-static const char kUserScriptHead[] = "(function (unsafeWindow) {\n";
-static const char kUserScriptTail[] = "\n})(window);";
-
 int UserScriptSlave::GetIsolatedWorldIdForExtension(const Extension* extension,
                                                     WebFrame* frame) {
   static int g_next_isolated_world_id =
       ExtensionsRendererClient::Get()->GetLowestIsolatedWorldId();
 
+  int id = 0;
   IsolatedWorldMap::iterator iter = isolated_world_ids_.find(extension->id());
   if (iter != isolated_world_ids_.end()) {
-    // We need to set the isolated world origin and CSP even if it's not a new
-    // world since these are stored per frame, and we might not have used this
-    // isolated world in this frame before.
-    frame->setIsolatedWorldSecurityOrigin(
-        iter->second, WebSecurityOrigin::create(extension->url()));
-    frame->setIsolatedWorldContentSecurityPolicy(
-        iter->second,
-        WebString::fromUTF8(CSPInfo::GetContentSecurityPolicy(extension)));
-    return iter->second;
+    id = iter->second;
+  } else {
+    id = g_next_isolated_world_id++;
+    // This map will tend to pile up over time, but realistically, you're never
+    // going to have enough extensions for it to matter.
+    isolated_world_ids_[extension->id()] = id;
   }
 
-  int new_id = g_next_isolated_world_id;
-  ++g_next_isolated_world_id;
-
-  // This map will tend to pile up over time, but realistically, you're never
-  // going to have enough extensions for it to matter.
-  isolated_world_ids_[extension->id()] = new_id;
+  // We need to set the isolated world origin and CSP even if it's not a new
+  // world since these are stored per frame, and we might not have used this
+  // isolated world in this frame before.
   frame->setIsolatedWorldSecurityOrigin(
-      new_id, WebSecurityOrigin::create(extension->url()));
+      id, WebSecurityOrigin::create(extension->url()));
   frame->setIsolatedWorldContentSecurityPolicy(
-      new_id,
-      WebString::fromUTF8(CSPInfo::GetContentSecurityPolicy(extension)));
-  return new_id;
+      id, WebString::fromUTF8(CSPInfo::GetContentSecurityPolicy(extension)));
+
+  return id;
 }
 
 std::string UserScriptSlave::GetExtensionIdForIsolatedWorld(
@@ -99,9 +78,7 @@ void UserScriptSlave::RemoveIsolatedWorld(const std::string& extension_id) {
 }
 
 UserScriptSlave::UserScriptSlave(const ExtensionSet* extensions)
-    : script_deleter_(&scripts_), extensions_(extensions) {
-  api_js_ = ResourceBundle::GetSharedInstance().GetRawDataResource(
-      IDR_GREASEMONKEY_API_JS);
+    : extensions_(extensions) {
 }
 
 UserScriptSlave::~UserScriptSlave() {
@@ -109,14 +86,23 @@ UserScriptSlave::~UserScriptSlave() {
 
 void UserScriptSlave::GetActiveExtensions(
     std::set<std::string>* extension_ids) {
-  for (size_t i = 0; i < scripts_.size(); ++i) {
-    DCHECK(!scripts_[i]->extension_id().empty());
-    extension_ids->insert(scripts_[i]->extension_id());
+  DCHECK(extension_ids);
+  for (ScopedVector<ScriptInjection>::const_iterator iter =
+           script_injections_.begin();
+       iter != script_injections_.end();
+       ++iter) {
+    DCHECK(!(*iter)->extension_id().empty());
+    extension_ids->insert((*iter)->extension_id());
   }
 }
 
+const Extension* UserScriptSlave::GetExtension(
+    const std::string& extension_id) {
+  return extensions_->GetByID(extension_id);
+}
+
 bool UserScriptSlave::UpdateScripts(base::SharedMemoryHandle shared_memory) {
-  scripts_.clear();
+  script_injections_.clear();
 
   bool only_inject_incognito =
       ExtensionsRendererClient::Get()->IsIncognitoProcess();
@@ -144,10 +130,9 @@ bool UserScriptSlave::UpdateScripts(base::SharedMemoryHandle shared_memory) {
   PickleIterator iter(pickle);
   CHECK(pickle.ReadUInt64(&iter, &num_scripts));
 
-  scripts_.reserve(num_scripts);
+  script_injections_.reserve(num_scripts);
   for (uint64 i = 0; i < num_scripts; ++i) {
-    scripts_.push_back(new UserScript());
-    UserScript* script = scripts_.back();
+    scoped_ptr<UserScript> script(new UserScript());
     script->Unpickle(pickle, &iter);
 
     // Note that this is a pointer into shared memory. We don't own it. It gets
@@ -168,11 +153,10 @@ bool UserScriptSlave::UpdateScripts(base::SharedMemoryHandle shared_memory) {
           base::StringPiece(body, body_length));
     }
 
-    if (only_inject_incognito && !script->is_incognito_enabled()) {
-      // This script shouldn't run in an incognito tab.
-      delete script;
-      scripts_.pop_back();
-    }
+    if (only_inject_incognito && !script->is_incognito_enabled())
+      continue; // This script shouldn't run in an incognito tab.
+
+    script_injections_.push_back(new ScriptInjection(script.Pass(), this));
   }
 
   return true;
@@ -180,145 +164,70 @@ bool UserScriptSlave::UpdateScripts(base::SharedMemoryHandle shared_memory) {
 
 void UserScriptSlave::InjectScripts(WebFrame* frame,
                                     UserScript::RunLocation location) {
-  GURL data_source_url = ScriptContext::GetDataSourceURLForFrame(frame);
-  if (data_source_url.is_empty())
+  GURL document_url = ScriptInjection::GetDocumentUrlForFrame(frame);
+  if (document_url.is_empty())
     return;
 
-  if (frame->isViewSourceModeEnabled())
-    data_source_url = GURL(content::kViewSourceScheme + std::string(":") +
-                           data_source_url.spec());
-
-  base::ElapsedTimer timer;
-  int num_css = 0;
-  int num_scripts = 0;
-
-  ExecutingScriptsMap extensions_executing_scripts;
-
-  blink::WebFrame* top_frame = frame->top();
   content::RenderView* top_render_view =
-      content::RenderView::FromWebView(top_frame->view());
+      content::RenderView::FromWebView(frame->top()->view());
 
-  for (size_t i = 0; i < scripts_.size(); ++i) {
-    std::vector<WebScriptSource> sources;
-    UserScript* script = scripts_[i];
-
-    if (frame->parent() && !script->match_all_frames())
-      continue;  // Only match subframes if the script declared it wanted to.
-
-    const Extension* extension = extensions_->GetByID(script->extension_id());
-
-    // Since extension info is sent separately from user script info, they can
-    // be out of sync. We just ignore this situation.
-    if (!extension)
+  ScriptInjection::ScriptsRunInfo scripts_run_info;
+  for (ScopedVector<ScriptInjection>::const_iterator iter =
+           script_injections_.begin();
+       iter != script_injections_.end();
+       ++iter) {
+    ScriptInjection* injection = *iter;
+    if (!injection->WantsToRun(frame, location, document_url))
       continue;
 
-    const GURL& document_url = ScriptContext::GetEffectiveDocumentURL(
-        frame, data_source_url, script->match_about_blank());
-
-    // Content scripts are not tab-specific.
-    const int kNoTabId = -1;
-    // We don't have a process id in this context.
-    const int kNoProcessId = -1;
-    if (!PermissionsData::CanExecuteScriptOnPage(extension,
-                                                 document_url,
-                                                 top_frame->document().url(),
-                                                 kNoTabId,
-                                                 script,
-                                                 kNoProcessId,
-                                                 NULL)) {
-      continue;
-    }
+    const Extension* extension = GetExtension(injection->extension_id());
+    DCHECK(extension);
 
-    if (location == UserScript::DOCUMENT_START) {
-      num_css += script->css_scripts().size();
-      for (UserScript::FileList::const_iterator iter =
-               script->css_scripts().begin();
-           iter != script->css_scripts().end();
-           ++iter) {
-        frame->document().insertStyleSheet(
-            WebString::fromUTF8(iter->GetContent().as_string()));
-      }
-    }
-
-    if (script->run_location() == location) {
+    if (PermissionsData::RequiresActionForScriptExecution(extension)) {
       // TODO(rdevlin.cronin): Right now, this is just a notification, but soon
       // we should block without user consent.
-      if (PermissionsData::RequiresActionForScriptExecution(extension)) {
-        top_render_view->Send(
-            new ExtensionHostMsg_NotifyExtensionScriptExecution(
-                top_render_view->GetRoutingID(),
-                extension->id(),
-                top_render_view->GetPageId()));
-      }
-      num_scripts += script->js_scripts().size();
-      for (size_t j = 0; j < script->js_scripts().size(); ++j) {
-        UserScript::File& file = script->js_scripts()[j];
-        std::string content = file.GetContent().as_string();
-
-        // We add this dumb function wrapper for standalone user script to
-        // emulate what Greasemonkey does.
-        // TODO(aa): I think that maybe "is_standalone" scripts don't exist
-        // anymore. Investigate.
-        if (script->is_standalone() || script->emulate_greasemonkey()) {
-          content.insert(0, kUserScriptHead);
-          content += kUserScriptTail;
-        }
-        sources.push_back(
-            WebScriptSource(WebString::fromUTF8(content), file.url()));
-      }
+      top_render_view->Send(
+          new ExtensionHostMsg_NotifyExtensionScriptExecution(
+              top_render_view->GetRoutingID(),
+              extension->id(),
+              top_render_view->GetPageId()));
     }
 
-    if (!sources.empty()) {
-      // Emulate Greasemonkey API for scripts that were converted to extensions
-      // and "standalone" user scripts.
-      if (script->is_standalone() || script->emulate_greasemonkey()) {
-        sources.insert(
-            sources.begin(),
-            WebScriptSource(WebString::fromUTF8(api_js_.as_string())));
-      }
-
-      int isolated_world_id = GetIsolatedWorldIdForExtension(extension, frame);
-
-      base::ElapsedTimer exec_timer;
-      DOMActivityLogger::AttachToWorld(isolated_world_id, extension->id());
-      frame->executeScriptInIsolatedWorld(isolated_world_id,
-                                          &sources.front(),
-                                          sources.size(),
-                                          EXTENSION_GROUP_CONTENT_SCRIPTS);
-      UMA_HISTOGRAM_TIMES("Extensions.InjectScriptTime", exec_timer.Elapsed());
-
-      for (std::vector<WebScriptSource>::const_iterator iter = sources.begin();
-           iter != sources.end();
-           ++iter) {
-        extensions_executing_scripts[extension->id()].insert(
-            GURL(iter->url).path());
-      }
-    }
+    injection->Inject(frame, location, &scripts_run_info);
   }
 
+  LogScriptsRun(frame, location, scripts_run_info);
+}
+
+void UserScriptSlave::LogScriptsRun(
+    blink::WebFrame* frame,
+    UserScript::RunLocation location,
+    const ScriptInjection::ScriptsRunInfo& info) {
   // Notify the browser if any extensions are now executing scripts.
-  if (!extensions_executing_scripts.empty()) {
-    top_render_view->Send(new ExtensionHostMsg_ContentScriptsExecuting(
-        top_render_view->GetRoutingID(),
-        extensions_executing_scripts,
-        top_render_view->GetPageId(),
-        ScriptContext::GetDataSourceURLForFrame(top_frame)));
+  if (!info.executing_scripts.empty()) {
+    content::RenderView* render_view =
+        content::RenderView::FromWebView(frame->view());
+    render_view->Send(new ExtensionHostMsg_ContentScriptsExecuting(
+        render_view->GetRoutingID(),
+        info.executing_scripts,
+        render_view->GetPageId(),
+        ScriptContext::GetDataSourceURLForFrame(frame)));
   }
 
-  // Log debug info.
   if (location == UserScript::DOCUMENT_START) {
-    UMA_HISTOGRAM_COUNTS_100("Extensions.InjectStart_CssCount", num_css);
-    UMA_HISTOGRAM_COUNTS_100("Extensions.InjectStart_ScriptCount", num_scripts);
-    if (num_css || num_scripts)
-      UMA_HISTOGRAM_TIMES("Extensions.InjectStart_Time", timer.Elapsed());
+    UMA_HISTOGRAM_COUNTS_100("Extensions.InjectStart_CssCount",
+                             info.num_css);
+    UMA_HISTOGRAM_COUNTS_100("Extensions.InjectStart_ScriptCount", info.num_js);
+    if (info.num_css || info.num_js)
+      UMA_HISTOGRAM_TIMES("Extensions.InjectStart_Time", info.timer.Elapsed());
   } else if (location == UserScript::DOCUMENT_END) {
-    UMA_HISTOGRAM_COUNTS_100("Extensions.InjectEnd_ScriptCount", num_scripts);
-    if (num_scripts)
-      UMA_HISTOGRAM_TIMES("Extensions.InjectEnd_Time", timer.Elapsed());
+    UMA_HISTOGRAM_COUNTS_100("Extensions.InjectEnd_ScriptCount", info.num_js);
+    if (info.num_js)
+      UMA_HISTOGRAM_TIMES("Extensions.InjectEnd_Time", info.timer.Elapsed());
   } else if (location == UserScript::DOCUMENT_IDLE) {
-    UMA_HISTOGRAM_COUNTS_100("Extensions.InjectIdle_ScriptCount", num_scripts);
-    if (num_scripts)
-      UMA_HISTOGRAM_TIMES("Extensions.InjectIdle_Time", timer.Elapsed());
+    UMA_HISTOGRAM_COUNTS_100("Extensions.InjectIdle_ScriptCount", info.num_js);
+    if (info.num_js)
+      UMA_HISTOGRAM_TIMES("Extensions.InjectIdle_Time", info.timer.Elapsed());
   } else {
     NOTREACHED();
   }
diff --git a/extensions/renderer/user_script_slave.h b/extensions/renderer/user_script_slave.h
index fc3da79..4dd1029 100644
--- a/extensions/renderer/user_script_slave.h
+++ b/extensions/renderer/user_script_slave.h
@@ -10,12 +10,14 @@
 #include <string>
 #include <vector>
 
+#include "base/memory/linked_ptr.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/memory/scoped_vector.h"
 #include "base/memory/shared_memory.h"
-#include "base/stl_util.h"
 #include "base/strings/string_piece.h"
 #include "extensions/common/user_script.h"
-#include "third_party/WebKit/public/web/WebScriptSource.h"
+#include "extensions/renderer/script_injection.h"
+#include "third_party/WebKit/public/platform/WebString.h"
 
 class GURL;
 
@@ -23,7 +25,9 @@ namespace blink {
 class WebFrame;
 }
 
-using blink::WebScriptSource;
+namespace content {
+class RenderView;
+}
 
 namespace extensions {
 class Extension;
@@ -38,14 +42,12 @@ class UserScriptSlave {
   // Returns the unique set of extension IDs this UserScriptSlave knows about.
   void GetActiveExtensions(std::set<std::string>* extension_ids);
 
+  // Gets the extension with the given |id|, if one exists.
+  const Extension* GetExtension(const std::string& extension_id);
+
   // Update the parsed scripts from shared memory.
   bool UpdateScripts(base::SharedMemoryHandle shared_memory);
 
-  // Inject the appropriate scripts into a frame based on its URL.
-  // TODO(aa): Extract a UserScriptFrame interface out of this to improve
-  // testability.
-  void InjectScripts(blink::WebFrame* frame, UserScript::RunLocation location);
-
   // Gets the isolated world ID to use for the given |extension| in the given
   // |frame|. If no isolated world has been created for that extension,
   // one will be created and initialized.
@@ -59,16 +61,23 @@ class UserScriptSlave {
 
   void RemoveIsolatedWorld(const std::string& extension_id);
 
+  // Inject the appropriate scripts into a frame based on its URL.
+  // TODO(aa): Extract a UserScriptFrame interface out of this to improve
+  // testability.
+  void InjectScripts(blink::WebFrame* frame, UserScript::RunLocation location);
+
  private:
+  // Log the data from scripts being run, including doing UMA and notifying the
+  // browser.
+  void LogScriptsRun(blink::WebFrame* frame,
+                     UserScript::RunLocation location,
+                     const ScriptInjection::ScriptsRunInfo& info);
+
   // Shared memory containing raw script data.
   scoped_ptr<base::SharedMemory> shared_memory_;
 
-  // Parsed script data.
-  std::vector<UserScript*> scripts_;
-  STLElementDeleter<std::vector<UserScript*> > script_deleter_;
-
-  // Greasemonkey API source that is injected with the scripts.
-  base::StringPiece api_js_;
+  // Parsed script data, ready to inject.
+  ScopedVector<ScriptInjection> script_injections_;
 
   // Extension metadata.
   const ExtensionSet* extensions_;