Revert of Stop copying script contents for each RenderFrames.

extensions/renderer/user_script_injector.cc

Index: extensions/renderer/user_script_injector.cc
diff --git a/extensions/renderer/user_script_injector.cc b/extensions/renderer/user_script_injector.cc
index 5800edf024370586840b842deddb856933b65c09..8ae1c164cb64e2e8b8f3d268065b2871dd103e72 100644
--- a/extensions/renderer/user_script_injector.cc
+++ b/extensions/renderer/user_script_injector.cc
@@ -44,6 +44,11 @@
 
 using RoutingInfoMap = std::map<RoutingInfoKey, bool>;
 
+// 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);";
+
 // A map records whether a given |script_id| from a webview-added user script
 // is allowed to inject on the render of given |routing_id|.
 // Once a script is added, the decision of whether or not allowed to inject
@@ -86,7 +91,6 @@
                                        UserScriptSet* script_list,
                                        bool is_declarative)
     : script_(script),
-      user_script_set_(script_list),
       script_id_(script_->id()),
       host_id_(script_->host_id()),
       is_declarative_(is_declarative),
@@ -202,19 +206,35 @@
   DCHECK_EQ(script_->run_location(), run_location);
 
   const UserScript::FileList& js_scripts = script_->js_scripts();
-  sources.reserve(js_scripts.size() +
-                  (script_->emulate_greasemonkey() ? 1 : 0));
+  sources.reserve(js_scripts.size());
+  for (const std::unique_ptr<UserScript::File>& file : js_scripts) {
+    base::StringPiece script_content = file->GetContent();
+    blink::WebString source;
+    if (script_->emulate_greasemonkey()) {
+      // We add this dumb function wrapper for user scripts to emulate what
+      // Greasemonkey does. |script_content| becomes:
+      // concat(kUserScriptHead, script_content, kUserScriptTail).
+      std::string content;
+      content.reserve(strlen(kUserScriptHead) + script_content.length() +
+                      strlen(kUserScriptTail));
+      content.append(kUserScriptHead);
+      script_content.AppendToString(&content);
+      content.append(kUserScriptTail);
+      // TODO(lazyboy): |content| is copied to |source|, should be avoided.
+      // Investigate if we can leverage WebString's cheap copying mechanism
+      // somehow.
+      source = blink::WebString::fromUTF8(content);
+    } else {
+      source = blink::WebString::fromUTF8(script_content.data(),
+                                          script_content.length());
+    }
+    sources.push_back(blink::WebScriptSource(source, file->url()));
+  }
 
   // Emulate Greasemonkey API for scripts that were converted to extension
   // user scripts.
   if (script_->emulate_greasemonkey())
-    sources.push_back(g_greasemonkey_api.Get().GetSource());
-
-  for (const std::unique_ptr<UserScript::File>& file : js_scripts) {
-    sources.push_back(blink::WebScriptSource(
-        user_script_set_->GetJsSource(*file, script_->emulate_greasemonkey()),
-        file->url()));
-  }
+    sources.insert(sources.begin(), g_greasemonkey_api.Get().GetSource());
 
   return sources;
 }
@@ -229,8 +249,14 @@
 
   const UserScript::FileList& css_scripts = script_->css_scripts();
   sources.reserve(css_scripts.size());
-  for (const std::unique_ptr<UserScript::File>& file : script_->css_scripts())
-    sources.push_back(user_script_set_->GetCssSource(*file));
+  for (const std::unique_ptr<UserScript::File>& file : script_->css_scripts()) {
+    // TODO(lazyboy): |css_content| string is copied into blink::WebString for
+    // every frame in the current renderer process. Avoid the copy, possibly by
+    // only performing the copy once.
+    base::StringPiece css_content = file->GetContent();
+    sources.push_back(
+        blink::WebString::fromUTF8(css_content.data(), css_content.length()));
+  }
   return sources;
 }